Add sections on locking and remote shares to unix/windows

This comes after several reports on the mailing lists of NFS
and CIFS installs failing.
Add extlink alias to create links to the right OMERO-*-virtual job
Fix virtual appliance link using newly defined extlink
Improve wording under system-requirements
Remove extra spaces on build system links.
Merge pull request #225 from sbesson/jenkins_stable_renaming

Jenkins stable renaming
Taking out indents causing purple block quote styling from plone stylesheets
Correct single typo in Importing data
Migrate the VM installation instructions to the Sphinx documentation
Fix headings and definitions lists
Minor fixes suggested by Roger & Kenny
Remove trailing whitespaces
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 224 (Training material)
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 227 (Add sections on locking and remote shares to unix/windows)
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 229 (Virtualjob extlink)
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 230 (Remove extra spaces on build system links.)
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken: PR 231 (Migrate the VM installation instructions to the Sphinx documentation)
merge dev_4_4 -D org -I include -E conflict -E needs-fixes -E broken

Repository: openmicroscopy/ome-documentation
Updating 858e9f2..18ba805
Merged PRs:
  # PR 224 gusferguson 'Training material'
  # PR 227 joshmoore 'Add sections on locking and remote shares to unix/windows'
  # PR 229 sbesson 'Virtualjob extlink'
  # PR 230 mtbc 'Remove extra spaces on build system links.'
  # PR 231 sbesson 'Migrate the VM installation instructions to the Sphinx documentation'

Generated by OMERO-merge-stable#132 (http://hudson.openmicroscopy.org.uk/job/OMERO-merge-stable/132/)