#2146 A testing framework for attribute conversion

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20198 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2183 Fixinf output of Potts, broken due to this ticket

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20200 b5f69653-2bf5-0310-8201-b0dafb8e1405