Add Design and add Loader and Save classes

src/main/scala/de/tobias/playpad/server/project/Design.scala

src/main/scala/de/tobias/playpad/server/project/Pad.scala

...ias/playpad/server/project/loader/json/DesignLoader.scala

...tobias/playpad/server/project/loader/json/PadLoader.scala

...bias/playpad/server/project/loader/sql/DesignLoader.scala

.../tobias/playpad/server/project/loader/sql/PadLoader.scala

...tobias/playpad/server/project/loader/sql/PathLoader.scala

...obias/playpad/server/project/saver/json/DesignSaver.scala

...e/tobias/playpad/server/project/saver/json/PadSaver.scala

...tobias/playpad/server/project/saver/sql/DesignSaver.scala

...de/tobias/playpad/server/project/saver/sql/PadSaver.scala

...cala/de/tobias/playpad/server/project/utils/JsonDef.scala

...scala/de/tobias/playpad/server/project/utils/SqlDef.scala

...ain/scala/de/tobias/playpad/server/server/SqlHelper.scala

...r/server/project/sync/listener/path/PathAddListener.scala

...erver/project/sync/listener/path/PathUpdateListener.scala