#2542 Added example to .dat file format description

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21774 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2542 Modified example of .dat file format description

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21777 b5f69653-2bf5-0310-8201-b0dafb8e1405