xserver-common: start Xsession when starting Xserver

* since this commit
  commit 305038f932fbcb39f3bb6698f8fad18172c30962
  Author: Jonathan Liu <net147@gmail.com>
  Date:   Wed Jun 12 08:30:15 2013 +0000
    xserver-nodm-init: do not execute Xsession twice

  xserver-nodm-init wasn't working correctly when it was used together
  with xserver-common which doesn't start Xsession from Xserver (unlike
  x11-common in oe-core).

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
recipes: Remove PR = r0 from all recipes

* Remove all PR = "r0" from all .bb files in meta-oe repo. This was done
  with the command sed -e '/^PR.*=.*r0\"/d' meta*/recipes*/*/*.bb -i

* We've switching to the PR server, PR bumps are no longer needed and
  this saves people either accidentally bumping them or forgetting to
  remove the lines (r0 is the default anyway).

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>