Update C++ job descriptions
Improving Unix guide usability
Avoid suggesting higher Python version.
Move the note about Python 3 support.
Add Josh's suggestion.
Make it clearer that envvars must be updated
Fix some unescaped \'s
Fixing UNIX install doc re:ICE etc
Douglas' comments + Windows Ice clarification
Fixing Roger's comments
Merge pull request #706 from hflynn/BF-CI-fix

Update C++ job descriptions
Merge pull request #707 from hflynn/rebased/develop/install

Updates to sysadmin installation docs (rebased onto develop)
Fixing ICE_HOME example in unix install
Add postgres check before brew install
Don't set ICE_CONFIG if no file exists
Removing ICE_HOME setting from unix install
Merge pull request #709 from will-moore/homebrew_install_edits

Homebrew install edits
Change the table of supported Ice/OMERO versions.

Note Debian 6.0 supports ends in May 2014 and provided ice-3.3. Restricting the supported versions to 5.0 instad of 5.x gives us the opportunity to drop ice-3.3 if we wish.
Reformat table
Merge pull request #714 from manics/rebased/develop/linux_versions

Update supported Linux versions for 5.0 (rebased onto develop)