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/ClientUser.js

@@ -327,6 +327,16 @@ class ClientUser extends Structures.get('User') {
     return this.client.api.users('@me').channels.post({ data })
       .then(res => this.client.channels.add(res));
   }
+
+  toJSON() {
+    return super.toJSON({
+      friends: false,
+      blocked: false,
+      notes: false,
+      settings: false,
+      guildSettings: false,
+    });
+  }
 }
 
 module.exports = ClientUser;