Update ch.cam.ac.uk references in custom reg checks

A number of Chemistry packages use a custom reg check with e.g. HLKM\software\ch.cam.ac.uk\WPKG\softwarename. This has been useful when none of the other wpkg <check> possibilities would work, and so I've just recorded a version number in that reg key. The use of ch.cam.ac.uk is entirely arbitrary, and we should aim to move away from it.

@cm214 I propose we replace such references with HKLM\software\ucam_wpkg.cam.ac.uk\softwarename .