Add links to CVODE installation instructions from tutorial

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21012 b5f69653-2bf5-0310-8201-b0dafb8e1405
Fix parallel failures from #2441/r29065 and #2488/r20993

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21015 b5f69653-2bf5-0310-8201-b0dafb8e1405