Partials (#3070)

* Remove GroupDMChannels

they sparked no joy

* Start partials for message deletion

* MessageUpdate partials

* Add partials as an opt-in client option

* Add fetch() to Message

* Message.author should never be undefined

* Fix channels being the wrong type

* Allow fetching channels

* Refactor and add reaction add partials

* Reaction remove partials

* Check for emoji first

* fix message fetching

janky

* User partials in audit logs

* refactor overwrite code

* guild member partials

* partials as a whitelist

* document GuildMember#fetch

* fix: check whether a structure is a partial, not whether cache is true

* typings: Updated for latest commit (#3075)

* partials: fix messageUpdate behaviour (now "old" message can be partial)

* partials: add warnings and docs

* partials: add partials to index.yml

* partials: tighten "partial" definitions

* partials: fix embed-only messages counting as partials

src/index.js

@@ -65,7 +65,6 @@ module.exports = {
   Collector: require('./structures/interfaces/Collector'),
   DMChannel: require('./structures/DMChannel'),
   Emoji: require('./structures/Emoji'),
-  GroupDMChannel: require('./structures/GroupDMChannel'),
   Guild: require('./structures/Guild'),
   GuildAuditLogs: require('./structures/GuildAuditLogs'),
   GuildChannel: require('./structures/GuildChannel'),