Delete gstlal files and cuda patch.
This MR deletes gstlal code and the cuda patch, repeating changes from !226 (closed).
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.
Edited by Timothy Davies