Fix some relative paths.

The robots.txt and favicon.ico locations were specified as relative
paths, which should have been changed since the location of the start
script changed relative to everything else. Hopefully, these paths are
specified correctly now and shouldn't need to be fixed in the future.
Merge branch 'master' of github.com:LMFDB/lmfdb
Merge branch 'master' of github.com:LMFDB/lmfdb
Fixed the bug I just introduced.
Merge branch 'master' of github.com:LMFDB/lmfdb
Merge branch 'master' of git://github.com/lemurell/lmfdb