Marking more granular than object level is difficult to implement

[terrymacdonald]

It is difficult to mark objects at a more granular level than object level at present (ie. 50% of this object is TLP White, 50% of this same object is TLP red).

We need to find a different solution. One potential solution is proposed below:

1. Remove Handling/Marking from STIX_Package Header
2. Remove the concept of XPath Controlled_Structure
3. Find a new home for Information Source, outside of Handling/Marking
4. Create Simple Marking, TLP, and TOU marking as either attributes to each object or as elements within each object

This issue is related to #377 and #378

[johnwunder]

It's not clear to me how these solutions will help with the problem?