Add Date header to every http response

Because why not?  Might want to add some cache hints, too, but those are
a bit more dynamic.
Make a json model for format
Restore views.html.static.pages to a Map

Using def m = x.toMap will reconstruct the map every time, which is less
efficient than just doing a list lookup.  On the other hand, the added
cost of the json construction is constant so unimportant.

Also use toString for json rather than stringify: stringify
pretty-prints with newlines and formatting.
Merge branch 'angular' of github:databrary/databrary into angular
Merge branch 'master' into angular