* Add grouping of preconditions to allow for flexible precondition logic.

* Fix checking Module Preconditions twice (and none of the command's own)

* Fix command preconditions group 0 looping over every other precondition anyway #whoopsies

* Use custom message when a non-zero Precondition Group fails.

* Fix doc comment rendering.

* Refactor loops into local function

* Considering a new result type

* Switch to IReadOnlyCollection<T> and fix compiler errors

* Revert PreconditionResult -> IResult in return types - Change PreconditionResult to a class that PreconditionGroupResult inherits.

* Feedback on property name.

* Change grouping type int -> string

* Explicitly use an ordinal StringComparer

* Full stops on error messages

* Remove some sillyness.

* Remove unneeded using.

Change wording of permission preconditions

Forgot a var >_>

Gladly taking suggestions for a better comments.

Also fix an issue where RequireBotPermission may throw if used in a
non-guild channel which required guild permissions.

Remove IUser.CreateDMChannelAsync / Fix SocketGlobalUser.DMChannel

Remove wrong parameter from FFMPEG audio example

Add newest verification level

Fixed exemple calling old non existing function.

Update the example precondition to use IServiceProvider

Update cmd docs to use IServiceProvider

* Update intro.md

* Update intro.md

* Update intro.md

* Update intro.md

* Update intro.md

* Update intro.md

* Update intro.md

Added/clarified some comments in structure.cs

Fix spelling

Users must have a verified phone on their Discord account.

http://i.imgur.com/BexDgzS.png

Update the quickstart structure example to rc3.

This parameter was samples per frame but changed to bitrate. (1920 is a way to low bitrate :) )

Parameter preconditions were always getting the empty service provider,
even when a custom one was provided in ExecuteAsync, which means that
preconditions which use services cannot work properly.

Remove CommandService.BuildServiceCollection

💥

This was 👍'd in the dev chat, I forgot to make a PR for it (whoops!)

* Made GetOrCreateUser always call AddRef and added check to PRESENCE_UPDATE to avoid readding users who have been removed from guilds

* Removed AddRef as per dev guild discussion