Support setting %graph_notebook_vis_options from variable

[michaelnchin]

Issue #, if available: N/A

Description of changes:

• Added the --store-to option to %graph_notebook_vis_options.
• Added support for setting %graph_notebook_vis_options from the value of a local variable, via either cell variable injection or the new --load-from line argument.

Example usage

Define a JSON serializable dict or string variable with your vis settings:

vis_options_var = {"physics": {"disablePhysicsAfterInitialSimulation": True, "simulationDuration": 2000}}

Then use the variable to set %graph_notebook_vis_options via either:

1. Cell magic variable

%%graph_notebook_vis_options
${vis_options_var}

2. --load-from

%graph_notebook_vis_options --load-from vis_options_var

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.