Allow use of TOSCA types by short name in the TOSCA template

Let user access TOSCA normative types by referencing it's short name in the
TOSCA service template. For example, tosca.nodes.Compute should be accessible
by specifying just Compute.

Change-Id: I448699895c2cd533835f94bca9fbc34a3712fbcf
Closes-Bug: #1349588