Refactor JSON serialiable class pattern

Change the JSON seriasiable data classes to use an explicit static
fromJSON method and an optional toJSON method for turning them to and
from JSON.

This improves over the previous pattern of passing the JSON to the
constructor as it frees up the constructor to be able to take whichever
argument types suits the code instead of being beholden to the JSON
serialised form.

packages/controller/src/ControlConnection.js

@@ -385,7 +385,7 @@ class ControlConnection extends BaseConnection {
 	}
 
 	async createModPackRequestHandler(message) {
-		let modPack = new libData.ModPack(message.data.mod_pack);
+		let modPack = libData.ModPack.fromJSON(message.data.mod_pack);
 		if (this._controller.modPacks.has(modPack.id)) {
 			throw new libErrors.RequestError(`Mod pack with ID ${modPack.id} already exist`);
 		}
@@ -394,7 +394,7 @@ class ControlConnection extends BaseConnection {
 	}
 
 	async updateModPackRequestHandler(message) {
-		let modPack = new libData.ModPack(message.data.mod_pack);
+		let modPack = libData.ModPack.fromJSON(message.data.mod_pack);
 		if (!this._controller.modPacks.has(modPack.id)) {
 			throw new libErrors.RequestError(`Mod pack with ID ${modPack.id} does not exist`);
 		}