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/client/BaseClient.js

@@ -105,6 +105,10 @@ class BaseClient extends EventEmitter {
     clearInterval(interval);
     this._intervals.delete(interval);
   }
+
+  toJSON(...props) {
+    return Util.flatten(this, { domain: false }, ...props);
+  }
 }
 
 module.exports = BaseClient;