Improved rotation and image reset

I've been using a modified version of 0.4.6 for a long time, so I decided to polish my additions and add them to the official version :smiley: 

- The "image reset" function now toggles between the original size and the natural size
- Fixed rotation for arbitrary angles (only multiples of 90° were working properly)
- Added the ability to rotate an image using the scroll wheel + a modifier key
  - Added the options in the GUI to select the modifier key(s) and the angle increment
  - Added the english label for those options to every locale, except for spanish, which are translated