Inital Attempt at pidFile Support in sddm.conf configuration file

Users should be able to specify a pidfile at compile time.
The default is /run/sddm.pid

fix crash on double pam handle free

fixes sddm/sddm#145

Fix build deps

Search for user specific config path and merge with the default config

Better guard against null values in user config

If the user set background cannot be loaded fall back to the default one

Fix xauth annoying error