Blueprint tools

As a spinoff from the discussion in [this issue](https://github.com/FAForever/fa/pull/571#issuecomment-95206272), we need a blueprint toolkit (here in faftools, or a new repo) that does the following:
- Parses unit blueprints
- Validates a set of blueprints against a specific ruleset
- Optionally modifies blueprints and persists the changes

Modifying the blueprints (Either using a comment or an actual value) for use by this toolkit would be acceptable in my mind.