Squash commits of branch feature/hikari:
- Introduce HikariCP as connection pool
- Log change
- Close maintenance stores correctly
- Do not force minimum number of connections
- Log change
- Assert stores are closed correctly
... and test QueryableStoreDeletionHandler
- Fix license
- Fix unit tests
- Use constants
- Change change log
- Move hikari version to libraries
- Enhance documentation
- Use configuration for pool settings