Add project list, current, open to web api

...Core/src/main/java/de/tobias/playpad/project/Project.java

...obias/playpad/plugin/api/websocket/MethodExecutable.scala

...obias/playpad/plugin/api/websocket/WebSocketHandler.scala

...tobias/playpad/plugin/api/websocket/message/Message.scala

...d/plugin/api/websocket/methods/ProjectCurrentMethod.scala

...ypad/plugin/api/websocket/methods/ProjectListMethod.scala

...ypad/plugin/api/websocket/methods/ProjectOpenMethod.scala

...ad/plugin/api/websocket/serialize/ProjectSerializer.scala