Backport TAXII 1.1 field names to messages_10

[MarkDavidson]

Processing TAXII 1.0 and TAXII 1.1 Poll Requests currently requires separate code paths because some variables are close-but-not-quite, or are not present in TAXII 1.0 but could be reasonably defaulted to certain values.

This issue proposes the following changes to TAXII 1.0 Poll Requests

• adding a collection_name field that is an alias to feed_name
• adding a poll_parameters property from messages_11.PollParameters that uses the defaults plus content_bindings=poll_request.content_bindings

This can be monkey-patched in code that uses libtaxii by performing the following:

if poll_request.version == tc.VID_TAXII_XML_10:
    poll_request.collection_name = poll_request.feed_name
    poll_request.poll_parameters = messages_11.PollParameters(content_bindings=poll_request.content_bindings)

Then code can treat Poll Request 1.0 and Poll Request 1.1 objects the same way.

Thank you.
-Mark

(Updated 3x since original posting)