Batchout

- Components refactored into dependency-free std package and ext packages available as extras
- Basic CLI for using YAML config, available as extra
- Documentation with auto-generated reference for registered components
- Added support for documents with nested indexing using Map component
- Added RegexExtractor, FileInput, CsvOutput

- Added new elements: Selectors for SQL-powered data filtering, Tasks for finer execution control;
- Reimplemented Data class using in-memory SQLiteDB;
- Added parameters for HTTP Input;
- Added Postgres Input (also with parameters);
- Removed Kafka Input;
- Reworked soundcloud_likes example making it a better showcase for latest features added.