This changes around `utils/use_require.js` to be able to generate any
of AMD (RequireJS), CommonJS, SystemJS, or UMD modules. The three
former also include support for translating `vnc.html`, producing a full
"app" version of noVNC.
This commit moves all the input-related files from `core/`
to `core/input/`, and renames a couple as relevant
(input.js --> input/devices.js, keyboard.js --> input/util.js).
This commit restructures noVNC, splitting it into the core directory
and the app directory, with the former containing core noVNC parts,
and the latter containing parts specific to the application.
Solly Ross