this was the name change i always wanted

This adds the following property to ITextChannel
- SlowMode (int)

The SlowMode field defines the time in seconds users must wait between
sending messages; if zero, slow-mode is disabled.

Bots are not affected by slow-mode, and as such, no changes need to be
made to the REST client's internal ratelimiting. This is strictly a
read/write cosmetic property for bots.

+ 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.

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

* InvalidPathChars does not exist in NS1.3; replaced with GetInvalidPathChars instead.

Discord no longer treats channels prefixed with 'nsfw' as NSFW,
so we no longer need to have this check.

* Fix #995 ICategoryChannel.CategoryID throws NotSupportedException

* Add tests

* change run mode of TestChannelCategories

* Add throw for GetCategoryAsync

* Add xml doc explaining why exception is thrown

* Add test coverage for text and voice channel categories

* initial implementation of INestedChannel

* more implementation of INestedChannel design

* Add case in RestChannel Create for Category type

* set the CategoryID for RestVoiceChannel

* rewrite channel category tests to work with existing pattern

* remove outdated todo

* Make IVoiceChannel implement INestedChannel

* remove redundant interface implementation

* Add c#7 feature from feedback

* Remove redundant GetCategoryAsync methods from socket entities

* Added configureawait to async methods

* change signature of interface GetCategoryAsync

* Add check for cachemode in rest channel GetCategory

* remove redundant IGuildChannel interface from ITextChannel and IVoiceChannel

* Update deps, fix test warnings.

* Support ns2.0

* Fix typo

* Remove ns1.1 support

* Net.Http and Net.Websockets.Client are not needed in ns2.0

* Move to net46 per volt

* Remove ns1.3 constants

* Implement DeleteMessageAsync

* Refer to MessageHelper instead of duplicating call

* Fix refactor error

commit 114e5b431b
Author: HelpfulStranger999 <helpfulstranger999@gmail.com>
Date:   Sat Apr 28 19:08:35 2018 -0500

    Fixes lack of default value for tts

commit 1fd8c70c53
Author: HelpfulStranger999 <helpfulstranger999@gmail.com>
Date:   Sat Apr 28 15:21:11 2018 -0500

    Makes text parameter of sending messages optional

commit a8bafb90cd
Merge: f38dd4c4 7e04285e
Author: WamWooWam <wamwoowam@gmail.com>
Date:   Mon Mar 12 08:05:52 2018 +0000

    Merge branch 'dev' of https://github.com/WamWooWam/Discord.Net into dev

commit f38dd4c421
Author: WamWooWam <wamwoowam@gmail.com>
Date:   Mon Mar 12 08:05:49 2018 +0000

    Cleaned up & fixed code style.

commit 7e04285e5d
Author: Thomas May <wamwoowam@gmail.com>
Date:   Sun Mar 11 14:11:28 2018 +0000

    Revert changes to DefaultRestClient

    Didn't actually need to change this, whoops.

commit 3f5b2c8ef1
Author: WamWooWam <wamwoowam@gmail.com>
Date:   Sat Mar 10 19:30:44 2018 +0000

    Enabled embeds alongside uploaded files.

    God damn Discord is a mess.

Co-authored-by: WamWooWam <wamwoowam@gmail.com>

* 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.

IChannel.IsNsfw will now return false when being used on any channel
that is not an ITextChannel. When being used on an ITextChannel, this
will now account for the API flag, and fall back to the channel name.

(this is gross design, thanks discord)