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/GuildMember.js

@@ -168,7 +168,7 @@ class GuildMember extends Base {
 
   /**
    * The overall set of permissions for this member, taking only roles into account
-   * @type {Permissions}
+   * @type {ReadOnly<Permissions>}
    * @readonly
    */
   get permissions() {
@@ -209,7 +209,7 @@ class GuildMember extends Base {
    * Returns `channel.permissionsFor(guildMember)`. Returns permissions for a member in a guild channel,
    * taking into account roles and 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);
@@ -230,16 +230,6 @@ class GuildMember extends Base {
     return this.roles.some(r => r.permissions.has(permission, checkAdmin));
   }
 
-  /**
-   * Checks whether the roles of this member allows them to perform specific actions, and lists any missing permissions.
-   * @param {PermissionResolvable} permissions The permissions to check for
-   * @param {boolean} [explicit=false] Whether to require the member to explicitly have the exact permissions
-   * @returns {PermissionResolvable[]}
-   */
-  missingPermissions(permissions, explicit = false) {
-    return this.permissions.missing(permissions, explicit);
-  }
-
   /**
    * The data for editing a guild member.
    * @typedef {Object} GuildMemberEditData