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/MessageEmbed.js

@@ -302,6 +302,10 @@ class MessageEmbed {
     return this;
   }
 
+  toJSON() {
+    return Util.flatten(this, { hexColor: true });
+  }
+
   /**
    * Transforms the embed object to be processed.
    * @returns {Object} The raw data of this embed