Add `phosh-pim` and re-organize packages

The current phosh-tablet package feels awkward as it depends on GNOME packages which are useful on any device. It would be best to create into phosh-pim which would pull contacts/calendar/tasks management apps, and make the latter a dependency of phosh-full.

phosh-tablet is kept as it may still be useful in the future, but now only depends on phosh-core.

phosh-phone, on the other hand, should depend only on phone-specific components (calls/SMS/MMS) and pull in phosh-pim as well as PIM is an important part of phone usage.

phosh-full now depends only on phosh-pim and suggests phosh-phone, without making it a dependency or recommend, so that the latter must always be explicitly installed on devices where it's relevant.