Argos will first try the given config file (given either with `--config` or with
`ARGOS_YAML_FILE` env var), then `argos-config.yaml`, then `/etc/argos/config.yaml`.
- Restructured server module to separate the application creation and configuration.
- Moved code dealing with SQLAlchemy database
setup and teardown to the main application file.
- Moved functions related to configuration file loading to `argos.server.settings`.
- Fixed SQLAchemy expressions in `argos.server.queries`.
- Implemented a more granular system of setting checks' schedule on the server.
- Introduced frequency scheduling on per-website basis in the YAML config.
- Introduced Pytest fixtures for handling test database and authorized HTTP client in `tests/conftest.py`.
- Included a first test for the api
- Implemented changes to models to accommodate changes to task scheduling.
- Fixed errors concerning database concurrency arising from changes to the application setup.
