ADD: Gimp batch converter to deal with gimp files. (EXP)
Fixes #14 : Gimp file converter using gimp, functional to flatten xcf,psd

Calligraconvert does a good work in general but some psd and xcf files
are read without masks or in a strange way.
If gimp is installed it will be used for convert files using script fu
functions. no bz2 support for now.
Fix: Fixes collage regresion. paths passing wrong values
ADD: Calligra convert accepts 2 new args, outputext and output dir
FIX: output ora and kra now preserve layers from xcf,psd,kra and ora

CHANGE: rename function can take a dictionary for setting output

REMOVED: original calligra convert function. this was invoked just
before the end, causing flattened output.

CHANGE: On rare ocasions inkscape cries and breaks loops when it
actually succeeded. Update error handling to act like Calligraerror
FIX: Inkscape wont validate using error codes as it always sends NONE
Back to if catch
ADD: Progressbar. Users needs some input after pressing convert.
Ver: 1.6, gimp backend, progress bar.