Merge pull request #774 from will-moore/custom_web_login_11961

Custom web login 11961
Remove deprecated virtual_job extlink
Remove all references to the CI builds from the official documentation
Remove references to JENKINS_JOB in the main Readme
Add documentation after extlink
merge dev_5_0 -D org: PR 777 (Remove all references to CI jobs in the official documentation (rebased onto dev_5_0))
merge dev_5_0 -D org

Repository: openmicroscopy/ome-documentation
Updating d6dbce6..cc1b343
Merged PRs (fast-forward):
  # PR 774 will-moore 'Custom web login 11961'

Merged PRs:
  # PR 777 sbesson 'Remove all references to CI jobs in the official documentation (rebased onto dev_5_0)'

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