Upload v1

- [x] New `/upload/v1` endpoint
- [x] Support for lcov uploading via `Content-Type: text/lcov`
- [x] Depreciate `/+` endpoint, continue support, provide depreciation notice
- [x] Update [codecov-python](https://github.com/codecov/codecov-python) package with new endpoints
- [x] New `/docs` for uploading documentation