Documenting 'make support'

[PrasadBabarendaGamage]

From conversations with Hugh:

The make support is mentioned when you configure the build. This happens fairly early on and as you say is kind of swamped in the output when you are doing a setup build.

First thing is to know that the 'make support' command has to be run from 'OPENCMISS_ROOT/build/manage/release'.

[hsorby]

This might be better placed to have this in the documentation repository, or at least part of it. I don't think this is directly to do with the setup script.