Cumulative API updates.

Created by: Neuheit

Summary

Fixes #432 (closed), and adds a variety of updates from the API.

Details

The bulk of the changes were made to the DiscordGuild class, with the addition of the properties/endpoints mentioned there, as well as the addition of properties added in the server "Discovery" update, which were the PreferredLocale, PublicUpdatesChannel, and the RulesChannel.

The minor changes included adding support for an guild region change in the audit logs, adding this to a variety of properties in DiscordClient, XML documentation updates, as well as fixing a null ref exception being thrown on startup.

Changes proposed

• Added all properties from issue #432 (closed)
• Added guild discovery properties.
• Added support for the region change in getting audit logs.
• Fixed a variety of style preferences, such as adding more this and fixing XML documentation
• Fixed a minor null ref being caught on startup.