Added rotation
Added saving and loading of bitmaps (only .jpg; needs to be expanded) and added LayerBitmap class
Corrected some bugs in the rotation algorithm

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Added support for importing and exporting PNGs, GIFs and BMPs

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Added a tool to move layers
Also changed the about dialog message

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>