Pushed to 1.9

- Added watermark alignment buttons for top-center, center-left,
center-right, bottom-center (thanks to @Walt9Z)
- It's now possible to resize both dimension but keeping the aspect
ratio. In this case, the pixel width/height
are treated as maximum sizes for the resulting image. (issue #25)
(thanks to @Walt9Z)
- Resize and Crop manipulations are now treated as "normal priority"
steps. Originally they started first, now they follow
the original order given by the user in the GUI (issue #53)
- Added "tall" smartphone screen Crop presets (for devices like iPhone
5+)
- JPEG subsampling settings was wrong (issue #52)
- Updated Italian translation