new preview generation modes, now fast_f is default (better performance/quality trade-off -- more browser scaling, less mush), more tweaking...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>
makeImageGID(...) now working, some refactoring and cleanup...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>