Fix documentations that were incorrect or missing (#1837)

* Fix docs for Guild#pruneMembers

* ClientApplication returns

* Guild#deleteEmoji

* Guild#setRolePosition takes RoleResolvable

* Client#fetchApplication returns ClientApplication not Oauth2Application

* ClientDataResolver#resolveImage can return null

* ClientApplication#toString small example

* Guild#allowDMs now has a only for user accounts warning

* ClientUserSettings#patch is private and setGuildPosition has a user account warning

* Role#setPermissions can take PermissionResolvable, not just String

* ChannelCreationOverwrites is for a role or a member, not for a "group"

* Fix ChannelData#userlimit string being wrong
"The user limit of voice the channel" :lul:

* ChannelResolvable is only for Channel or Snowflake

* EmojiIdentifierResolvable supports Snowflakes

* UserResolvable doesn't take a guild

* Make patch functions private

* Remove examples

* Webhoox#edit options.name defaults to the webhook name

* Make VoiceConnection functions private

* Am dum
The whole ClientUserSettings category is only for self bots soo

* Value for update functions is *

* Make update functions be private

* Fix GuildEditData missing Ssytemchannel property

* PermissionOverwriteOptions can accept null as an option
(Why did no-one document this?)

src/client/Client.js

@@ -394,7 +394,7 @@ class Client extends EventEmitter {
   /**
    * Obtains the OAuth Application of the bot from Discord.
    * @param {Snowflake} [id='@me'] ID of application to fetch
-   * @returns {Promise<OAuth2Application>}
+   * @returns {Promise<ClientApplication>}
    */
   fetchApplication(id = '@me') {
     return this.api.oauth2.applications(id).get()