Should check for condition attribute when Observable is in an Indicator

[johnwunder]

When an observable is included in an Indicator, each of the property fields should have a condition attribute set. We probably wouldn't be able to catch every instance of this (in particular if an observable is referenced via @idref but might be able to catch a bunch.

[bworrell]

This was implemented in some capacity in 9d0b7f0. It doesn't handle multiple levels of referencing--only dereferencing Observable @idref attributes on Observables held within an Indicator instance.

Does not:

• Dereference Observables referenced from within other Observables
• Does not dereference Objects, Actions, Events, etc.