new database vacuuming behaviour, new feature for vacuuming db, plugin menu changes
	modified:   CHANGELOG_HISTORY
	modified:   create_db.py
	modified:   import_data_to_db.py
	modified:   metadata.txt
	modified:   midvatten.py
	modified:   midvatten_utils.py
	modified:   resources.py
	modified:   resources.qrc