Bugfix: Github issue #649.

Bugfix for __Issue #649 with psds and smart sprite sheets.__

### Please add to 1.1 branch(Kept it in one commit to keep cherrypicking simpler)

Republishing for a unchanged already published smart spritesheet caused the fllelookup to be overwritten without the renaming rules.
Solution: Sprite sheet operation create an intermediate filelookup file in the smartsheet folder which is then loaded and merged with all other lookups and intermediate lookups.
Intermediate filelookups are deleted if smartsheet flag is removed from folder.