Add gst upgrade scripts.
Changes
This MR add scripts to highlight incompatible gstreamer 0.10 code (from gstlal).
These were considered during the upgrade, and could be useful in future, but it would be harmless to remove them.
This repeats all changes from !226 (closed) for these files.
Purpose
I intend to split !226 (closed)'s changes into a number of MRs, which won't be functional code versions themselves, but once complete will encompass the full set of changes to upgrade to py3.
This should provide useful code diffs for reviewers.