TASK-1201 - Simple viewer for App Spec files

[briehl]

This introduces a new function for creating an app cell from either a spec.json and display.yaml, or a pre-validated and merged spec (i.e. those that get returned from Narrative Method Store).

Used as follows:

from biokbase.narrative.appeditor import generate_app_cell

Use 1.

my_spec_json = "stringified JSON from an app spec that was copied into a cell"
my_display_yaml = "like above but yaml"
generate_app_cell(spec_tuple=("test_app", my_spec_json, my_display_yaml))

Use 2.

my_valid_spec = some_json_structure #see NarrativeMethodStore.get_method_spec to fetch one, or NarrativeMethodStore.validate_method to make one from a spec.json and display.yaml
generate_app_cell(validated_spec=my_valid_spec)

Either case will plop the App Cell into place after execution. No promises as to how well it functions, but you can see the results without going all in and registering, refreshing, etc.

[coveralls]

Coverage increased (+0.02%) to 12.239% when pulling aaaf994 on briehl:spec-editor into 464f78c on kbase:develop.

[coveralls]

Coverage increased (+0.02%) to 12.589% when pulling 458789e on briehl:spec-editor into 73aab3f on kbase:develop.