Policies to retire functionality
Draft of thorn and parameter retirement policies
At release time, the main Einstein Toolkit thornlist in the manifest  should only contain thorns that are supported and actively maintained. Thorns that do not meet these requirements are candidates for retirements.
In order to retire a thorn or parameter:
- it needs to be marked as deprecated for at least one release. Deprecation notices appear in the release announcement.
- for parameters we would like a means to mark them as deprecated in param.ccl (not implemented yet)
- thorns are to be marked as deprecated in the thornlist
- deprecated thorns are to be listed on the ET website
- In order for a thorn to be retired, no other active thorn's testsuite may depend on it, unless the test is designed to only test the to-be-retired thorn.
- Deprecating and finally retiring a thorn both needs to be result of a public discussion, usually on one of the public meetings (phone calls).