* Add ExplicitContentFilter property to Guild
* re-order properties to match order listed on api docs
* re-order SystemChannelId to match api docs
* Implement ApplicationId in Guild model
* Add ExplicitContentFilter property to Guild
* re-order properties to match order listed on api docs
* re-order SystemChannelId to match api docs
* Implement ApplicationId in Guild model
* Improve xmldoc for IGuild ExplicitContentFilter
* Update xmldoc
* docs "Id" -> "ID"
* rename Test.GuildPermissions to a more general Test.Guilds
* Add ExplicitContentFilter to GuildProperties
* Add a test for ExplicitContentFilterLevel modification behavior
* Implement ModifyAsync behavior
* simplify ExplicitContentFilter test
* Add RestGuild ApplicationId inheritdoc
* Implement message Activity and Application model update
* RestMessage Application and Activity implementation
* add ToString to MessageApplication
* Add IconUrl property to MessageApplication
* clean up whitespace
* another excessive whitespace removal
