Cpp: Remove C++ links which are no longer available

No alternative or replacement links exist at present,
therefore removing them entirely.
Group OMERO jobs with different Ice versions
Hardcode development branches for each version
Review documentation jobs description
Add documentation for 5.1 docs merge jobs
Merge pull request #618 from rleigh-dundee/cpp-link-removal-develop

Cpp: Remove C++ links which are no longer available
Merge pull request #608 from dpwrussell/plugin_backwards_compat

Backwards compatability instructions for web plugins
Merge pull request #612 from hflynn/rebased/develop/glencoe_link

Removing link to out-of-date Ice binaries at Glencoe (rebased onto develop)
merge develop -D org -I include -E exclude: PR 594 (Blitz api5 11852)
merge develop -D org -I include -E exclude: PR 596 (document extra values for omero.fs.repo.path_rules (ticket #10822))
merge develop -D org -I include -E exclude: PR 600 (New Continuous Integration jobs)
merge develop -D org -I include -E exclude: PR 605 (Small fixes from PR #603)
merge develop -D org -I include -E exclude: PR 606 (Server upgrade bugfix (rebased onto develop))
merge develop -D org -I include -E exclude: PR 613 (Modify the root of the main OME CI server to use ci.openmicroscopy.org (rebased onto develop))