add consts to loader and saver

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

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

...as/playpad/server/project/loader/json/ProjectLoader.scala

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

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

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

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

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

...bias/playpad/server/project/saver/json/ProjectSaver.scala

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

...e/tobias/playpad/server/project/saver/sql/PageSaver.scala

...obias/playpad/server/project/saver/sql/ProjectSaver.scala

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

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