Better html visualization of API data

[haz]

Already have json/xml endpoints, but would be nice to have a visual representation of a database entry.

So instead of this...

http://api.planning.domains/json/classical/problem/123

...we'd have this:

http://api.planning.domains/html/classical/problem/123

Viable starting point: https://simplecss.org/

The variety of pages we'll need, can be found through this interface: https://api.planning.domains/#interface