refactor(BitField): base class for Permissions, ActivityFlags, Speaking (#2765)

* abstract BitField from Permissions

* reduce useless code, improve docs

* add a ReadOnly identifier to the return type of Bitfield#freeze()

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-1.html#partial-readonly-record-and-pick

* fix the RangeError

* update docs, convert Speaking and ActivityFlags to bitfields

* fix some docs

* Fix Speaking BitField oops

* docs for oops

* more incorrect docs

* Fix incorrectly named property

* add new classes to index

* fix missing @extends docs

* default bitfield resolve to 0, and cleanup defaulting everywhere

Also removes GuildMember#missiongPermissions() alias that had incorrect behavior

* Breaking: Rename Overwrite allowed and denied to allow and deny

To be consistent with the api's naming

* fix setSpeaking usage to bitfields instead of booleans

* fix speaking bug in playChunk

* docs: Updated typings

* fix: BitFieldResolvable should use RecursiveArray

* bugfix/requested change

* typings: Cleanup (#2)

* typings: Fix BitField#{toArray,@@iterator} output type

* typings: correct PermissionOverwrites property names and nitpicks

src/index.js

@@ -10,12 +10,15 @@ module.exports = {
   WebhookClient: require('./client/WebhookClient'),
 
   // Utilities
+  ActivityFlags: require('./util/ActivityFlags'),
+  BitField: require('./util/BitField'),
   Collection: require('./util/Collection'),
   Constants: require('./util/Constants'),
   DataResolver: require('./util/DataResolver'),
   DataStore: require('./stores/DataStore'),
   DiscordAPIError: require('./rest/DiscordAPIError'),
   Permissions: require('./util/Permissions'),
+  Speaking: require('./util/Speaking'),
   Snowflake: require('./util/Snowflake'),
   SnowflakeUtil: require('./util/Snowflake'),
   Structures: require('./util/Structures'),