layerman: enable meta-multimedia

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
layers.txt: move meta-ti to track angstrom staging branch

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
layerman: mention layer in changelog

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
Merge remote-tracking branch 'origin/angstrom-v2012.05-yocto1.2'