API change: Mouse/kbd handling to include/input.js

API change: Mouse/kbd handling to include/input.js

API change: for intergrators that explicitly include the Javascript
files (that do not use include/vnc.js)js, include/input.js is a new
file that must also be included.

The mouse and keyboard handling could be useful on its own so split it
out into a Keyboard and Mouse class in include/input.js.

This refactoring is preparation to deal with issue #21 - non-US
keyboard layouts.