Restructure services

MR deals with just restructure of services into grouping by portfolio and some subgrouping where necessary. Most the work done in mkdocs.yml.

Puts templates in for new services. Actual content for these (and outdated existing services) needs updating - see #34 (closed) and https://gitlab.developers.cam.ac.uk/uis/devops/admin/-/issues/195

Closes: #59 (closed)