documents: Format title from URI if filename is not available

This may (ATM, will) be inaccessible data out of the tracker:Documents
graph. Avoid trying to make up for it in the SPARQL query, and handle
the title formatting in code if the filename info is missing.

Closes: #55
1 job for wip/hadess/better-title in 9 minutes and 23 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Test
passed flatpak:master #1223191
flatpak

00:09:23