rename ajax overlays to url overlays
introduce jsUri

I used a [fork by Denis Sokolov](https://github.com/SlikNL/jsUri/)
and used uglify-js to minify it.

We decided against [URI.js](https://github.com/medialize/URI.js)
because it is too large.
improve setting format to .overlay in overlay urls
trigger overlay on pageload
validate overlay path
manipulate addressbar when overlay state changes
error message for non-js users
Merge pull request #555 from xi/feature-553-link-to-overlays

Feature 553 link to overlays