Cleans and improves heat code path

Reasons:
- Heat code path contains cinder code.
- Heat code path contains nova code.
- Heat template is frozen with Volume support,
  it cannot act in a volume disabled environment.

Changes:
- Adds conditional Volume support in heat.template.
- Adds conditional template rendering.
- Cleans nova code from heat code path.
- Cleans cinder code from heat code path.

Change-Id: I7e4d6edf8bb11de0bcf913a58b257c625468322c
Closes-Bug: #1262378
Adds Missing _() for Exception Message Translation

Reasons:
- Exception messages missing underscores. This is necessary to
  mark messages as ready for translation, and is already the
  defacto standard across the trove codebase,as per,
  https://wiki.openstack.org/wiki/Translations
- Because of incorrect Exception messages, it does not overrides
  the default message of BadRequest.

Changes:
- Adds the missing underscore function to wrap a few user-facing
  exception messages.

Change-Id: Ib4a183f717146493e514b8169679a57cc2ecfd01
Closes-Bug: #1264688
Merge "Cleans and improves heat code path"
Merge "Adds Missing _() for Exception Message Translation"