Fixes issue #938, completes support for lirc_xbox

This completes out-of-box support for the Xbox 1 DVD dongle and lirc_xbox by:
-fixing the way lircd is started in lircd_helper
-blacklisting the xpad game controller driver
-adding an lircd.conf.xbox file with buttons appropriately named for XBMC
-installing that file to the /etc/lirc directory instead of the one from the lirc build
-adding udev support in 98-lircd.rules to support knockoffs

Should be a pretty clean fix with no harmful side-effects.

Fixes https://github.com/OpenELEC/OpenELEC.tv/issues/938