Adds tests for Heat

Tests and client methods for:
- template-show
- template-validate
- template-url-validate
- stack-list
- stack-show
- resource-list
- resource-show
- resource-metadata
- event-list
- event-show

Testing Neutron resources:
- network
- subnet
- router_interface

Testing server property:
- subnet_id

Change-Id: I47bb0dd653da51c9ff1d2ffe0b02c102cc0098d5
Merge "Adds tests for Heat"