Enable Non-Square Sprite Sheets

Resize width and height alternatively while packing images into
non-square sprite sheets
Merge pull request #648 from djh-/develop

Improve Texture Packing for Non-Square Sprite Sheets
Bugfix: Github issue #649.
Issue with psds and smart sprite sheets.
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.
Merge pull request #660 from NickyWeber/bugfix/1.1/#649_psd_filelookup_issue

Bugfix: Github issue #649.
Merge branch 'develop' of https://github.com/spritebuilder/SpriteBuilder into develop