Switch from /etc/aptitude-robot/options to /etc/aptitude-robot/options.d/

Also aptitude options can be better handled if they can be distributed
over multiple files. Because of that, we switch from the single file
/etc/aptitude-robot/options to a run-parts based directory at
/etc/aptitude-robot/options.d/.

The previously distributed options file was an empty example which
would not make much sense inside /etc/aptitude-robot/options.d/.

We now ship /etc/aptitude-robot/options.d/10-remove-level-maximum
containing "-o 'Aptitude::ProblemResolver::Remove-Level=maximum'"
which is considered a necessary safe-guard against accidentially
removing too many packages when resolving conflicts automatically.

Bump version to 1.2.14.