If PKCS1 parsing of the SSH key fails, try PKCS8
If no image is generated, just return nil for the Openstack provider

This mirrors what is done in other providers e.g. Amazon providers
Use generic Openstack endpoint criteria, not rackspace specific ones
Allow the Openstack project to be specified

It isn't actually optional, according to the spec
Merge branch 'generic_openstack'
Merge branch 'specify_openstack_project'
Merge branch 'try_parse_pkcs8'
Merge branch 'master' of https://github.com/mitchellh/packer