Add experiment metadata to the Environment object in the Store (#3967)
Add experiment metadata to the Environment object in the Store (#3967)

* Motivation for features / changes

  Certain variants of TensorBoard (TensorBoard.dev, for example) retrieve experiment metadata when loading the "Environment". We want to properly expose that as part of the `Environment` that we store in the ngrx store.

* Technical description of changes

  Add a few new properties to the `Environment` object. The data is already retrieved and stored by TensorBoard.dev - it just needs to be exposed officially in the internal API.

tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard,tensorflow/tensorboard