#2421 Calculate cell area for 2d in 3d. Also output cell labes as mutation states in mesh based VTUs 

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19727 b5f69653-2bf5-0310-8201-b0dafb8e1405
Repair Ozzy's vandalism

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19730 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2421 Fixing errors in r19727

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19731 b5f69653-2bf5-0310-8201-b0dafb8e1405