add drm connection manager

Signed-off-by: Mattias Andrée <maandree@operamail.com>
m + add list_screens_drm, rename list_screens to list_screens_randr and make list_screens run eiher list_screens_randr or list_screens_drm

Signed-off-by: Mattias Andrée <maandree@operamail.com>
update todo

Signed-off-by: Mattias Andrée <maandree@operamail.com>
add drm_get

Signed-off-by: Mattias Andrée <maandree@operamail.com>
add function for applying curves with drm

Signed-off-by: Mattias Andrée <maandree@operamail.com>
update todo

Signed-off-by: Mattias Andrée <maandree@operamail.com>