Move maintainer script to the libloc1 package

Move maintainer script to the libloc1 package

This makes sure that libloc1 can find the database from the
libloc-database package without needing to install the location package.
Also, as the location package transitively depends on libloc1, this
makes sure that /var/lib/location/ is cleaned up in case the cronjob in
the location package downloaded a database dump.

Also make libloc1 recommend libloc-database | location to make sure some
database is available by default. But don't make it a hard dependency as
one can provide a different path to libloc1 and also it would be a
cyclic dependency for the location package.