A: New URL scheme

This turns ```#storage-details?type=drive?id=Foo?machine=bar``` into ```#/bar/storage-details?type=drive?id=Foo```.

This is turned into ```#/bar/storage/drive/Foo``` when Storage becomes a external page in an iframe.

The next step is to remove the need for PageExternal.

See above, I think we should preserve the concept of an undefined host. So that parent frame can fill in null as appropriate.