setup-environment-internal: select machine from list
setup-environment-internal: select machine from list

If the user hasn't chosen a MACHINE, present an alphabetical list of known
machines from which they can choose (by number).

Signed-off-by: Trevor Woerner <8835777cd84fba3d7873eabbbe1f2de2d3f25b00@gmail.com>

koenkooi/angstrom-manifest,ndechesne/qcom-oe-manifest,linaro-home/lhg-oe-manifests,96boards/oe-rpb-manifest,Angstrom-distribution/angstrom-manifest,twoerner/angstrom-manifest