Choose tag wrapper combination

Add option in settings where user can choose tag wrapper combination keys : 

- CTRL + ALT left + KEY (or ALT right + KEY)  this is by default. ALT right is a shortcut for CTRL + ALT left
- ALT left + KEY

This is useful for non english qwerty keyboards where ALT right is used for specials characters.

Tested on IE9, Firefox, Chrome on Windows 7 with a french azerty keyboard.