Consider making cluster name optional in the API and generating a name

[tmckayus]

Currently oshinko-s2i tooling does random cluster name generation for on-demand cluster creation, but this could just as easily be done in oshinko-rest if we make the cluster name optional instead of required on create.

Instead of a validation error, a missing name would cause a random name generation. The generated name would be returned in the result, so the caller would have full knowledge of the name chosen.

Any name passed would still be respected.

[elmiko]

this is probably an improvement, plus we could then move some of the name scanning stuff in there as well. so, if a random name fails, it could try again before returning an error.

i'm ok with this. +1

[elmiko]

migrated to radanalyticsio/oshinko-cli#93