Experiment and model upload to GitLab via MLflow interface

This MR implements an experiment upload command that can upload models and artefacts for storage at GitLab.

doc/api.rst

@@ -97,6 +97,7 @@ Reusable auxiliary functions.
    :toctree: api/utils
 
    mednet.utils.checkpointer
+   mednet.utils.gitlab
    mednet.utils.rc
    mednet.utils.resources
    mednet.utils.tensorboard