Add option to export by a file containing a list of experiments or models

[amesar]

Instead of just accepting a comma-delimited list of object names to bulk export, enhance option to accept a file name.

export-experiments --experiments my-experiments.txt
export-models --models my-models.txt

where my-experiments.txt is:

/Users/me@my.com/experiments/sklearn_wine
/Users/me@my.com/experiments/keras_mnist