Fix bugs and enhance usability in image-plugin

Changes:
* Keep Aspect Ratio now works from the start if activated
* Keyboard-inputs for height/width are no longer auto-corrected when
  below minimum to avoid weird changes while still typing
* Toggling aspect ratio in crop-mode no longer breaks the plugin
* Field values are correctly updated after cropping and cancelling crop
* Gradually increasing size now works while keep aspect ratio is activated
* Several documentation fixes and minor refactoring
Fix image-demo by adding necessary paths
Fix bugs when resizing while keeping aspect-ratio

* Fixed problems when resizing and releasing mouse inside image
* Repaired toggle-button functionality
Fix internationalization in confirm-dialog
Enhance and fix characterpicker-plugin

* Overlay shows characters in the font-family/weight/style of the selected
  text
* If multiple characters are inserted, plugin now inserts them at the
  correct position
* The same focus is now used for mouse and keyboard commands
* Redesign of the CSS (making it smaller and removing white space)
* Adds a note in the guide concerning incorrectly displayed characters
Recompiling aloha.css to include characterpicker updates