Split modules logic

# Module names could be confusing
Imports such as `from src.config.config import ...` or `from src.downloader.downloader import ...` could confuse and we should split their logic between multiple files.

For example, we can split the config module into `neo4j_config`, `redis_config`, and `generic_config`.

src
-- config
---- neo4j_config
---- redis_config
---- generic_config