PTFM-8631: Add --property and --tag to dx find projects

--property and --tag behavior is also adjusted for dx find data to be
consistent.  "--property foo" now tests for presence of a property
called "foo", and multiple tags can be matched.

@kislyuk and @psung interest

I've changed the API of `dxpy.bindings.find_data_objects` by adding an argument "tags" and deprecating "tag" (throwing `DXError` if both are provided).

`dxpy.bindings.find_projects` now has a "tags" field with nothing else changed.