Create branches to support Morty (and eventually older yocto releases)

[fboudra]

Per #26

Some bits from oe-meta-go are now provided by oe-core master. These bits aren't available for released version of yocto project. In order to avoid to break users of the released versions, please create the needed branches.
It's a best practice to do so, see for example http://git.openembedded.org/openembedded-core/