Bbconf

**This release introduces backwards incompatible changes**
Changed
- switched to object-relational mapping approach (ORM) for database interface

Added
- added new fields in the bedfiles and bedsets schema

**This release introduces backwards incompatible changes**
Changed
- `BedBaseConf` backend (database) to [PostgreSQL](https://www.postgresql.org/)
- complete `BedBaseConf` class redesign

Added
- index deleting methods:
- `delete_bedsets_index`
- `delete_bedfiles_index`
- multiple new keys constants

Changed
- make `search_bedfiles` and `search_bedsets` methods return all hits by default instead of just 10. Parametrize it.
- added more arguments to `insert_bedfiles_data` and `insert_bedsets_data` method interfaces: `doc_id` and `force_update`
- Elasticsearch documents are inserted into the indices more securily, `insert_*` methods prevent documents duplication

Added
- initial project release