Add models for cloud orchestration

This PR is split from original PR #333  (to be discarded). It focus only on the models for orchestrations. 
The master PR #523 covers the design and progress of the support for orchestration including AWS CloudFormation and OpenStack Heat.
![orchestration](https://cloud.githubusercontent.com/assets/7047579/4719534/6144c4e0-592a-11e4-9dc1-7d882f00f947.png)

I find this column name strange.  Perhaps `content` is better?  It just reads funny...

Read

```ruby
OrchestrationTemplate.all.collect { |template| template.template }
```

vs.

```ruby
OrchestrationTemplate.all.collect { |template| template.content }
```