Add Path to Pad, Add Saver and Loader for path; code cleanup

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

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

...obias/playpad/server/project/loader/json/PathLoader.scala

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

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

...ias/playpad/server/project/loader/sql/ProjectLoader.scala

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

.../tobias/playpad/server/project/saver/json/PathSaver.scala

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

...e/tobias/playpad/server/project/saver/sql/PathSaver.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

...de/tobias/playpad/server/server/account/AccountPost.scala

...la/de/tobias/playpad/server/server/plugin/PluginGet.scala

...de/tobias/playpad/server/server/project/ProjectList.scala