Added new images for the extra keys
Added the extra keys Ctrl, Alt, Tab and Esc to the control bar.
Tweaked the media sizing rules to match the new buttons to the left.
Switched from using a list to absolute positions to achieve more
consistant behavior across different browsers.
Added variables for the keysums to make the code easier to read.
Added a new file for the key symbols, using the well recognized names for the constants from X11:
* The list is found in /usr/include/X11/keysymdef.h
* I did only include the most common symbols for now..
Merge branch 'master' of https://github.com/kanaka/noVNC into ctrlalttabesc

Conflicts:
	include/ui.js
	vnc.html
Merge pull request #284 from samhed/ctrlalttabesc

Support for extra keys such as Ctrl, Alt, Tab and Esc on mobile devices