Adds exception handling around heat stack creation

Reasons:
- heat_client.stacks.create raises HTTPException which was not
  captured in heat work-flow.

Changes:
- Adds heat_exceptions.HTTPException in the exceptions captured
  while stack creation.

Change-Id: Ia87e1f6d08ac062e1085dd1c0b0c4197a74597d4
Closes-Bug: #1325049
Add warnings when a path for api_extensions_path does not exist

This commit fixes api-paste factory to show warnings when the path
for api_extensions_path doesn't exist.

Change-Id: I2288e39d6740aabc7818c3c963257e700237afe5
Closes-Bug: #1301660
Add slave_of_id to instance model

Add new 'slave_of_id' field to instance model and schema.

partially implements blueprint replication-v1
Change-Id: I613eaed6057745f38ffffafad2c72a0338b2552a
Merge "Add slave_of_id to instance model"
Merge "Add warnings when a path for api_extensions_path does not exist"
Merge "Adds exception handling around heat stack creation"