+ Starting from this commit, all return types for tasks will use style similar to most documentations featured on docs.microsoft.com

References:
https://docs.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.dbcontext.-ctor?view=efcore-2.1
https://docs.microsoft.com/en-us/dotnet/api/system.io.filestream.readasync?view=netcore-2.1
https://docs.microsoft.com/en-us/dotnet/api/system.io.textwriter.writelineasync?view=netcore-2.1#System_IO_TextWriter_WriteLineAsync_System_Char___
And many more other asynchronous method documentations featured in the latest BCL.

* Mark guild as optional for invite

* Mark partial InviteMetadata members as Optional<T>

* Some of them aren't sent when requesting through the general GET invite endpoint

* Remove GetInviteParams

* It was kinda stupid in the first place, might as well always get the count instead of having to ask the user whether they want the two fields filled or not.

* Add ChannelType property

* Add vanity invite support

* Fix ' />' caused by Agent Smith oddities
* Fix styling to be more specific about the mention of IDs

* ConnectAsync(bool external) API implemented

This allows developers to handle the AudioClient externally (for example with Lavalink)

* Modify ConnectAsync API and add DisconnectAsync to IAudioChannel

* Update summary message on IAudioChannel.DisconnectAsync()

* Review changes:
- Fix `if (!external)` styling
- Remove unecessary ConnectAsync overload

* SocketVoiceChannel overload update

* Update IAudioChannel.ConnectAsync()
- Remove ConfigAction from parameters
- Add SelfDeafen/SelfMute to parameters

* Remove SocketVoiceChannel.ConnectAsync() default params (Inherit)

This reverts commit adf4da19fc.

Someone hasn't written c# in a while

commit 07bca5b31a
Author: Joe4evr <jii.geugten@gmail.com>
Date:   Fri Apr 6 09:44:50 2018 +0200

    Add ability to specify parameters on channel creation

* Copy audit logs impl from old branch and clean up

I suck at using git, so I'm gonna use brute force.

* Remove unnecessary TODOs

Category channels do not provide any new information, and the other
I forgot to remove beforehand

* Add invite update data, clean up after feedback

* Remove TODOs, add WebhookType enum for future use

WebhookType is a future-use type, as currently audit logs are the only
thing which may return it.

- Because DocFX sucks at rendering langword

* Set usage of TokenType.User as an error rather than a warning.

* Remove commented sections and #pragma's

Additionally, changes use of ReadMessages to ViewChannel since that Obsolete was also suppressed by the pragma

commit a85c5814a7
Author: Christopher F <computerizedtaco@gmail.com>
Date:   Sat Jan 6 22:25:48 2018 -0500

    Code cleanup

commit 4b243fd3dd
Author: Christopher F <computerizedtaco@gmail.com>
Date:   Sat Jan 6 22:08:28 2018 -0500

    Add support for channel categories (#907)

    commit 41ed9106f2
    Author: mrspits4ever <spits.lucas@gmail.com>
    Date:   Thu Dec 14 20:02:57 2017 +0100

        removed mentioning support for RestCategoryChannel, added channels property to SocketCategoryChannel

    commit 71142c3108
    Merge: 4589d731 678a7238
    Author: mrspits4ever <spits.lucas@gmail.com>
    Date:   Wed Dec 13 21:17:53 2017 +0100

        Merge branch 'dev' of https://github.com/RogueException/Discord.Net into feature/channel-categories

    commit 4589d73187
    Author: mrspits4ever <spits.lucas@gmail.com>
    Date:   Wed Dec 13 21:17:46 2017 +0100

        adressed requested changes

    commit d59b038efa
    Author: pegasy <pegasy@users.noreply.github.com>
    Date:   Mon Sep 25 18:53:23 2017 +0200

        Renamed classes / properties / methods to use CategoryChannel instead of ChannelCategory to be consistant with how text / voice channels are named.

    commit 5c4777dc8c
    Author: pegasy <pegasy@users.noreply.github.com>
    Date:   Sun Sep 24 19:08:25 2017 +0200

        removed Guild from class name for ChannelCategory
        Renamed all properties to use Category instead of Parent
        Throw exception on GetUsers / GetInvites etc for categories

    commit e18bd8c799
    Author: pegasy <pegasy@users.noreply.github.com>
    Date:   Sun Sep 24 15:49:51 2017 +0200

        Add support for channel categories (as its own channel type)

* Add Webhook API models, REST implementation, and Socket bridges.

* Remove token overrides from REST.

Leaving that as a Webhook package only feature.

* Add Webhook API models, REST implementation, and Socket bridges.

* Remove token overrides from REST.

Leaving that as a Webhook package only feature.

* Webhook core implementation.

* Webhook REST implementation.

* Webhook client implementation.

* Add channel bucket id.

* Implemented emoji endpoints.

* Fixed: now using API entities for REST client.

* Removed emoji listing endpoint, as per @foxbot's request.

* Changed Guild#DefaultChannel to resolve the first accessible channel

Resolves #776

This change is inline with hammerandchisel/discord-api-docs#329

RestGuild#DefaultChannelId is now obsolete and will throw a
NotSupportedException.

* RestGuild#DefaultChannelId will fall back to the guild ID

Adding an exception here would be a breaking change, so this was agreed
to fall back to the previous behavior, which would just return the guild
ID.

* Add support for audit log reasons

* Made changes per discussion