- Skip the 'type' property, since it shouldn't be overridden.
- Add info on default values (currently this is only used for timestamp
properties, setting them to the current time).
- Rename it to STIXPropertyDocumenter since they're called properties in
STIX instead of attributes.
Also remove package and module names from classes and functions.
Also remove stix2.base from docs. We hide all private classes and
functions from the docs, so the only thing the documentation for base
included was STIXJSONEncoder.
Note: The first cell in each .ipynb file contains code to suppress
tracebacks in output cells. Thus cells that generate exceptions will
only output the error, without the traceback, which makes the
documentation easier to read.