<bugfix>Fixed loading wrong abstraction DB version</bugfix> <bugfix>Fixed trying to write empty workflow list to DB</bugfix>
<bugfix>Fixed loading wrong abstraction DB version</bugfix>
<bugfix>Fixed trying to write empty workflow list to DB</bugfix>

db/services/io.py:
- open_vistrail_bundle_from_db:
  Read abstraction using vistrail db version
- save_vistrail_to_db:
  Skip writing workflows if list is empty

VisTrails/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,VisTrails/VisTrails,celiafish/VisTrails,Nikea/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,minesense/VisTrails,minesense/VisTrails,celiafish/VisTrails,minesense/VisTrails,Nikea/VisTrails,hjanime/VisTrails,VisTrails/VisTrails,minesense/VisTrails,Nikea/VisTrails,celiafish/VisTrails,hjanime/VisTrails,hjanime/VisTrails,minesense/VisTrails,celiafish/VisTrails,hjanime/VisTrails