Revamped gadget menu

Gadget menu changes:

• The "hold it to show the menu" gadget menu has been completely replaced by a control on your left hand that toggles a menu that sits in the room in front of you.
• Replace the concept of "installs" with "favorites". These are offered to you in the gadget menu. Using avcmd install will add that gadget to your favorites the next time you start Aardvark.
• Added a global gadget registry. If you want your gadget to appear in the registry, please submit a pull request against this file: https://github.com/aardvarkxr/gadget-registry/blob/master/registry.json
• Added a gadget scanner tool that appears when the gadget menu is up. Point this at a gadget to kill or favorite that gadget.

Other fixes:

• Fixed local storage and cookies not saving.