Add toJSON methods (#1859)

* tojson things

* fix client

* ignore private properties

* remove extra property descriptors

* handle primitive flattening

* remove unused import

* add toJSON to collections

* reduce stateful props

* state

* allow custom prop names when flattening

* fix client

* fix build

* fix flatten docs

* remove guild.available, cleanup permissions, remove arbitrary id reduction

* fix util import

* add valueOf as needed, update member props

* fix incorrect merge

* update permissionoverwrites and permissions

remove serialization of permissions in PermissionOverwrites#toJSON.
change Permissions#toJSON to serialize permissions, by default excluding
admin checks.

* change Permissions#toJSON to return the primitive

* Permissions#toJSON explicitly return bitfield

src/structures/MessageReaction.js

@@ -1,4 +1,5 @@
 const GuildEmoji = require('./GuildEmoji');
+const Util = require('../util/Util');
 const ReactionEmoji = require('./ReactionEmoji');
 const ReactionUserStore = require('../stores/ReactionUserStore');
 
@@ -55,6 +56,11 @@ class MessageReaction {
     return this._emoji;
   }
 
+
+  toJSON() {
+    return Util.flatten(this, { emoji: 'emojiID', message: 'messageID' });
+  }
+
   _add(user) {
     if (!this.users.has(user.id)) {
       this.users.set(user.id, user);