**Improvements**:
- 45 - CLI support of the new API
- CLI option `-l` to use the old frontend
- support date input in `%Y-%m-%d` format
- all dates will be returned in `%Y-%m-%d` format when using the new API
**Bufixes**:
- 46 - `tan_insert` option enforces the useage of old frontend
- CLI option `-l` enforces the useage of old frontend