Numerapi

- `stake_drain`: set drain flag correctly, so things will look less confusing
in the UI
- fix `SignalsAPI.upload_predictions`

- fix `SignalsAPI.ticker_universe`
- added `validationBmcMean` and `era.validationBmc` to diagnostics
- added `CyptoAPI`

- added `get_account_leaderboard` to fetch account-level leaderboard
- added 'models_of_account' to fetch all models of an account
- 'SignalsAPI.ticker_universe': stop using hardcoded URL
- remove `set_stake_type` - no longer relevant
- deprecate 'SignalsAPI.download_validation_data'
- code style fixes
- fix docs

- signals: add 'list_datasets' and 'download_dataset'

- add `bmcRep` and `mmcRep` to `get_leaderboard`

- fix `get_leaderboard`