Angular refactor

This isn't a complete refactor, but it is a start. Addresses #223.

Changes:
* Overrides Flask's template tags (`{{ }}` becomes `<% %>`), since Angular's are the ones that are used 99% of the time.
* Some organizational improvements in the directory structure.
* Flattens querybuilder by using scope inheritance rather than isolate scopes.
* Adds `ng-model` support for all VQB input types (like `<cpf>`).
add comment about how step doesn't create a child or isolate scope so you need to use it with something else that creates a child or isolated scope.