[sextante] fixed wrong import
Fix placement of simple markers in cached images
Reject features with empty geometry in QgsMapToolAddFeature
Add unique title input dialog for new and duplicate composers

- Allows user to title composer before creation (optionally based on existing composer titles)
- Helps limit duplicate titles
- Non-GUI generation of new and duplicate composers not restricted (unchanged)
- Duplicate composer slot now free of GUI interruptions
- Change from hiding of duplicate composer (during template loading) to pausing updates to give user feedback
Avoid crash where composer is deleted after spawning modal composer manager