layerman: switch more layers to angstrom staging branches

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
oebb.sh: put env file in PWD

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
README: update to match current status

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