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/util/Constants.js

@@ -367,15 +367,6 @@ exports.ActivityTypes = [
   'WATCHING',
 ];
 
-exports.ActivityFlags = {
-  INSTANCE: 1 << 0,
-  JOIN: 1 << 1,
-  SPECTATE: 1 << 2,
-  JOIN_REQUEST: 1 << 3,
-  SYNC: 1 << 4,
-  PLAY: 1 << 5,
-};
-
 exports.ChannelTypes = {
   TEXT: 0,
   DM: 1,