Improves Heat Demo Functionality

Previously, the Heat demo suffered from the following limitations:

1. The number of Nova instances to spawn and the image flavor were
   hard coded in the Heat template.

2. No outputs existed. This required users to run nova-list to
   obtain the IP's of VMs.

3. No documentation existed.

This patch addresses the above limitations.

Change-Id: I495aa9c73a91200c01cecc1719ee5532c1f6c9cb