doxygen for changes to mechanics

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19039 b5f69653-2bf5-0310-8201-b0dafb8e1405
More doxygen

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19040 b5f69653-2bf5-0310-8201-b0dafb8e1405
Parallel and Doxygen fixes

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19043 b5f69653-2bf5-0310-8201-b0dafb8e1405