tool to generate mustache templates

[sheppard]

As discussed in wq/wq#18, it would be nice to be able to have templates generated automatically based on the current model configuration.

Here's how I envision making this work:

1. Create template snippets for common field types (text, date, number, <input type=radio> for choice, <select> for foreign key)
2. Create a wq.start tool that reads an XLSForm and assembles a model class and an *_edit.html template (and the detail and list templates for good measure). The template would be generated once and placed in the templates/ folder so it could be customized and compiled into the offline app.
3. Create a wq.start tool that creates the same templates based off of a registered model. Reference the serializer fields rather than model fields since the serializer is what's actually processing the form, and it may have more/fewer fields than the model. (EDIT: split out from previous step)
4. Eventually, figure out a way to update (or at least validate) existing templates when new fields are added - e.g. "Your template is missing an <input> for the field ..." moved to tool to validate templates #23
5. Introduce an option in ./deploy.sh (or a similar process) to automatically generate and/or update templates during every build. This would facilitate the quick creation of simple CRUD applications that only need a model (like how the Django admin works).