Homebrew instalation command

Main goal of this PR is to fix the wrong Homebrew installation command (thanks @stick for noticing it) - see commit 4c2b874.

Added a number of commits fixing redirected links (see [linkcheck output](http://hudson.openmicroscopy.org.uk/job/OMERO-docs-merge-stable/ws/_build/linkcheck/output.txt) ). Linkcheck should still pass, hyperlinks should be unchanged and the size of output.txt reduced.