layerman: switch meta-minnow to 'dylan' and oe-core to angstrom-staging

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
layerman: fetch meta-ros

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>

Conflicts:
	sources/layers.txt