Add ability to import STIX bundles into analytic exchange

[j987987]

This could not be accomplished with a generic import STIX bundle feature, due to the following:

• Multiple meta properties are mapped to fake extended properties
• Sensors are mapped via fake relationships to abstract away data path complexity
• Sensors don't have data model
• Data path of sensors is not exported
• Possible merge problems with attack patterns

I would recommend ignoring sensors/data path for the time being, and simply focusing on getting the indicators and attack pattern relationships in there.

[infosec-alchemist]

I think limiting to indicators and attack patterns make sense to start with.

[ghost]

I also don't think it should be based on the whole stix collection being missing.