Disables all POSTs, optionally allowing users to log in (without updating last login date)
Blocked POSTs will redirect to the GET endpoint if possible, otherwise to referrer or in last case, home page.
API requests will get a plaintext message with 405 status code.
* Replace all `from nyaa import app` imports with `app = flask.current_app` (or `from flask import current_app as app` where possible)
* Add a separate config object for top-level and class statements as `nyaa.extensions.config`
Required because those codes don't have app context at the time of evaluation/execution.
* Remove `routes.py` file and register all blueprints in `nyaa/__init__.py`
* Refactor `nyaa/__init__.py` into an app factory
* Update tools
* Update tests (temporary, will be replaced)