several bug fixes (e.g. change of saved distributions, main_window.dataChanged() calls added, where needed)

updated create_database script, PRAGMA synchronous is now on and distribution is being saved in one transaction

updated create_database script, PRAGMA synchronous is now on and distribution is being saved in one transaction

PS: A lot of changes (I should be committing more often :/)

groupedit improved, now we need to solve deletion (may require a little overhaul on the flow of application :/)