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/structures/Role.js

@@ -54,7 +54,7 @@ class Role extends Base {
 
     /**
      * The permissions of the role
-     * @type {Permissions}
+     * @type {ReadOnly<Permissions>}
      */
     this.permissions = new Permissions(data.permissions).freeze();
 
@@ -203,7 +203,7 @@ class Role extends Base {
    * Returns `channel.permissionsFor(role)`. Returns permissions for a role in a guild channel,
    * taking into account permission overwrites.
    * @param {ChannelResolvable} channel The guild channel to use as context
-   * @returns {?Permissions}
+   * @returns {ReadOnly<Permissions>}
    */
   permissionsIn(channel) {
     channel = this.guild.channels.resolve(channel);