Elemental implementation of more Module objects

AT FIRST: This sucks^^
-added 4 "Last saved modules" to test the saving of more than one
module.
-added reset_modulecounter - Button: When pressing this one the counter
starts from the beginning and already created Modules get overwritten;
Also just handy for testing
-When saving a new Module in ModuleSettingsActivity a new Module gets
saved. The name of the SharedPreference in wich this Module is
permanently saved in is called "MODULE" + modulecounterposition.
-After pressing "Save" the previous Activity gets called

WARNING: The code got a bit confusing. It will become better!