Change new Datatype Properties and new Object Properties to the semex namespace from the stix namespace

[rhohimer]

When I first started implementing I put the properties in the stix namespace because the Incident class was stubbed in. However, the new properties are extensions.

[rhohimer]

1. I'll need to delete the assertions in the class definition of Incident
2. • Delete the Data Property definitions from the stix namespace
3. • Create the Data Property definitions in the semex namespace
4. • Reassert the properties in the Incident class definition

[rhohimer]

I still have a open question about stix:extension_type... this seems like a property that should remain in the stix namespace.

[rhohimer]

These changes were made in the "threat-incident-extensions" branch.