added my own waterdrop handlers and hooked them into wahlzeit;
updated handlers;
reverted default wahlzeit handlers;
added my own WaterdropPhotoFactory and hooked it in startup process of wahlzeit; reverted default Factory;
added new WaterdropType for type object pattern practice;
updated persistence for waterdrop types;
updated gui for waterdrop types;
started refactoring: want to use an own table for my waterdrops instead of merging it into the photo table;
updated WaterdropManagerTests;
added missing javadoc with methodtypes;
added design by contract preconditions to setter methods in waterdroptype;