weston-init: Add possibility to run weston as non-root user

weston-init: Add possibility to run weston as non-root user

These changes are from meta-96boards primarily
Launch the session via a udev rule based on what kind of display device
is available

delete weston-conf and move the fuctionality into weston-init other
layers are doing same

weston-init installs machine specific weston.ini therefore mark is
machine specific now

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>