Merge all scripts into one

[goued120]

Thanks for this useful script!

I needed to change it a bit to fit my needs, and I thought I would push it back in case you are interested in my edits.

Main changes are:

• all scripts merged into one (easier to maintain)
• added a 'preview' option to see what is sent to the printer without actually sending anything
• add more control on what to do when the image's aspect ratio does not match the expected one

I did not change any of the processing, so the end result should stay the same as in the original scripts.

What I could not test:

• sending several images to the printer at once (not sure the printer queue is properly handled)
• actually printing in a format other than postcard (it do not have any other format at hand right now)

The aspect ratio tolerance might have to be further adjusted (see todo in script).