Allow create_version_from_run() to take a run obj

[convoliution]

Because a method that says from_run() ought to be able to take a run.

Tests

$ pytest test_model_registry/test_model_version.py::TestMDBIntegration::test_from_run
==================================================== test session starts ====================================================
platform darwin -- Python 2.7.18, pytest-4.6.11, py-1.10.0, pluggy-0.13.1
rootdir: /Users/miliu/Documents/modeldb/client/verta/tests, inifile: pytest.ini
plugins: hypothesis-4.57.1
collected 1 item                                                                                                            

test_model_registry/test_model_version.py .                                                                           [100%]

=========================================== 1 passed, 4 warnings in 31.85 seconds ===========================================