Suggested tweaks to openssh_srv.xml

I've merged !21 (merged) so I can continue to review other MRs that were branched off from here, but I think the package could do with some modifications at some point

1. as it stands the package is only usable in maths. If that's the intention we might rename it maths-openssh or similar
2. with reference to the above, the package makes use of the WPKGWININFO env variable. I was hoping to implement automated testing to ensure we were using variable names from the "approved" list. Thus ideally this would be replaced by a reference to the %institute%-config folder on the IFS. But if need be the automated testing could have config to whitelist certain variable names in certain packages
3. strictly one of the comments is invalid XML because it lacks a space after the opening delimiter (i.e. <!-- rather than <!-- ). Most parsers are flexible on that bit of the XML spec but it's the sort of thing that can suddenly lead to odd problems!