[WIP] Convert Warehouse to Flask

This is still heavily WIP

- [x] Inherent from ``flask.Flask`` for our application object.
- [x] Convert views into blueprints and register them
- [x] Replace Flask session support with our own
- [x] Rework our CSRF to work under Flask
- [x] Remove the ability to use the ``g`` variable
- [ ] Restore the hostname whitelist
- [ ] Re-audit all of our security features
- [ ] Ensure Flask is not attempting to handle static files
- [ ] Ensure the template environment and contexts are sane
- [ ] Ensure none of the default configuration options are bad
- [ ] Audit Warehouse and all it's views to ensure that this hasn't broken any of our requirements
- [ ] Fix the tests to work correctly
- [ ] Write fixtures to enable sane unit testing of this mess

So this is what I have so far. The more I work with it the more it feels like I'm trying to fight the framework to prevent it from doing something stupid behind the scenes and I still think that the thread locals make everything less clear and harder to understand. However it's more or less working now, all that's really left to do is make sure Flask isn't doing more stupid things behind the scenes and to make sure I didn't break anything as well as fix the tests.