Heat template validation view

Currently, when we load a template in the orchestration view, the second panel project/stacks/select_template provides a form which can be modified. The issue is that we can modify value, but we have to check the template for the correct name i.e image_id. This is problematic because if one error is made we have to resubmit the form.

In addition Heat already provides all the options which can be modified with the template_validate method. This method return JSON datas which can be used for creating multi-choices in the form.

The goal of this blueprint is to build an html template based on the JSON provided by the valid template method of Heat.
Use select instead of input, to reduce the possibility of errors.