fetch.sh: Use --progress when cloning git repos.

This works around a bug when cloning slow repos with buildbot.
LAYERS: Replace 'obsolescent' oe-core.git with the proper openembedded-core.git repo.
LAYERS: Remove unnecessary meta-oe.git meta layer.

Was unused. See bblayers.conf.
Merge branch 'master' into measured

Conflicts:
	LAYERS
	conf/bblayers.conf