* Change all Select(... as ...) to OfType

* Add changes according to 194a8aa427

* Initial support for invite member count arg

* Fix IDiscordClient#GetInviteAsync behavior

- Previously, the GetInviteAsync method would return null since it couldn't be parsed as a simple RestInvite object. The object should be a RestInviteMetadata instead.

* Fix methods that didn't comply with the interface

* Change with_counts REST behaviour

* Remove unnecessary JSON prop

* Remove AcceptAsync

* Move REST requests to appropiate class

* Add call to ClientHelper and expose to public API

* Expose shard count request in public api

* Expose method from interface

* Update sharded client to utilize the new method

* Method is already implemented in a base class

* Refactor name to fit pattern for methods returning a `Task`

* Adds missing ConfigureAwait

* Corrects unnecessary whitespace

* Removes unneeded whitespace

This resolves #931

As part of this change, StreamingType has been refactored to realign
with how Discord seems to define the 'type' field on activities now.

StreamType is renamed to ActivityType, and the following properties have
been changed:
- NotStreaming -> Playing
- Twitch -> Streaming

Additionally, the StreamType property/parameter has been removed from
StreamingGame, and moved up a scope to Game.

Normal Games may now set their type, to line up with changes in
Discord's official clients.

This resolves #742.

Common cases for IGuild being null on access are DMs (since they do not
belong to a guild) - this change resolves null guilds to shard zero,
where DMs are also received.

* Add API-level support for Rich Presences

* Add library-level support for Game presences

* Add model conversions for outgoing+incoming rich presences

* Refactored Game into Activities

* Integrated Activities with user entities

rebase hell from 5f3cb947a9

* Fix JSON converters for Activities

* Finish rebase, activity should be set on BaseSocketClient

* Use ApplicationId to define a rich presence

* Added SetActivityAsync to Base and Sharded Socket clients

* Remove public parameterless Game constructor

* Remove GameAssets, refactored to GameAsset

* Hide constructors for types that should be read-only

* Revert changes to Discord.Net.sln

got damned visual studio caching

* Refactor GameParty to use dedicated current/capacity values

Per feedback from @khionu

* Add BaseDiscordClient. Add various missing RequestOptions args.

DiscordSocketClient and DiscordShardedClient's shared members now exist in this abstract class.

* Add ShardReady event.

* Style consistency. Remove extraneous overloads.

Remove extraneous overloads.

* Add BaseSocketClient#DownloadUsersAsync().

Style cleanups.

* Add ShardLatencyUpdated event.

Style cleanup.

* Hook LatencyUpdated for ShardedClient.

* Begone whitespace.

* I'm good at this, I swear. >_>

* Add back DiscordShardedClient.UserPresenceUpdated

* Add ObsoleteAttribute

* Removing the UserPresenceUpdated event.

Conflicts:
	src/Discord.Net.WebSocket/DiscordSocketClient.cs