A collapsible sidebar and more room to work

The admin area has had a fresh coat of paint. The sidebar collapses, the main section runs wider, and a few things have moved.

The admin controls have been redrawn. The left sidebar collapses when you want your screen back, and the main content area can run wider.

Public Page, Switch Organisation and Create New Organisation now live in your user menu at the top right, rather than the top left. Sorry about the muscle memory.