* Added selective frame tag export for Spritesheets
* Changes LinesCount value and max_value to canvas_size
This does not allow the spritesheet to contain more frames than the tag has, because it limits its size to the number of frames the currently selected tag has.
Co-authored-by: Manolis Papadeas <35376950+OverloadedOrama@users.noreply.github.com>
process_frame() was being called twice when the export dialog appeared, and the frame number was different than the one already stored in the export dialog
