lpqr/acpi-call: Drop acpi-call

Closes GH-3.
raring/bumblebee: Do not check for older version

We used to check for Bumblebee from MrMEEE and debian checked for debumblebee,
but both haven't see any use for months or even now years, and moreover both
have never been packaged for the currently supported distribution.
raring/bumblebee: Change bumblebee-nvidia section

Since this package depends on the proprietary nvidia driver, this should be in
contrib.
raring/primus: Minor changes to control

Some cosmetic changes in package descriptions, plus adding "metapackage" to
primus-nvidia description for fixing lintian warning properly.
raring/primus & raring/virtualgl: Some others cosmetic changes