Implement Q.Notices

[EGreg]

Right now, Q.Notices is implemented in QTools.js

Implement Q.Notices from scratch, with the methods add, remove, hide, show, and make the notices work correctly with server-side notices set by Q_Response, for the first page as well as subsequent pages loaded with Q.loadUrl().

Note that the add and remove methods should issue POST and DELETE requests to Q.url("Q/notice"), and you should implement the handler for POST.

The notices should appear and work as they do in SmartApp, on mobile, tablet and desktop.