Remove "dating site" from the FCD page title

Closes #67.
Add license info to footer (and larger detail text)

Fixes #66.
Allow negative integers (multitree IDs) in Browse page

The regexp validation here assumed positive integers in all cases, which didn't
work if a taxon name was entered directly in the simple-search field. In these
cases, the name is resolved to a multitree ID, which is a signed integer.

Fixes #68.