Blender Git Loki

fix for own error when trying to fix python command line crash,
was calling screenmain() before executing the python script which meant it was never executed (therefore no crash :) )

Moved screenmain() back to the the end of main() and added a TESTBASELIB_BGMODE which checks for G.vd and uses the scene layer if its not there. Of course python should not be running stuff that uses G.vd :/

Also made python scripts stay attached to screens when LOAD UI is disabled. This means you can load a new blend file and the python console can stay open, has been tested for a while in the apricot branch.