Some of baymodel attributes should be renamed for user-friendliness

[vikas choudhary]

magnum currently support creation of baymodel resource by both uuid and name of attributes but attribute names seems accepting uuids only which is not correct.For example,
magnum baymodel-create --name k8sbaymodel \
                       --image-id fedora-21-atomic-3 \
                       --keypair-id testkey \
                       --external-network-id public \
                       --dns-nameserver 8.8.8.8 \
                       --flavor-id m1.small \
                       --docker-volume-size 5 \
                       --coe kubernetes
for attributes image-id, keypair-id, external-network-id, flavor-id can accept both id and name.These should be renamed to image, keypair, external-network, flavor respectively.To do this changes may also be required to do in db model of baymodel also.

[Eli Qiao (taget-9)]

make as in-progress since assgnee is vikas.