Start work on 1:0.2.91
gpu-manager.c: use exists_not_empty()
gpu-manager.c, tests/gpu-manager.py: replace laptop semantics with offloading semantics

We now detect whether it makes sense to use RandR offloading without
having to check if we're dealing with a laptop.

We currently accept only Intel+AMD or Intel+NVIDIA combinations.

This will also make things a little better if users forgot to unplug
the cable from the integrated card.

Also, add build dependency on libdrm-dev.
gpu-manager.c: create or remove a file if we need to offload rendering

This will help nvidia-prime and reduce code duplication.
gpu-manager.c: rename has_card_connected_outputs() as has_driver_connected_outputs() and change its behaviour

We cannot rely on card0 being the integrated driver, therefore you run through all the possible drm devices.
debian/rules: remove /etc/init/hybrid-gfx.conf

Also remove the current upstart job from the architectures
that don't ship gpu-manager.
tests/ubuntu_drivers.py: do not abort if test_auto_install_system fails
Release 1:0.2.91