#2183 methods for adding population writers

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18567 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2228 / #2367 Add some more fake PETSc setups.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18570 b5f69653-2bf5-0310-8201-b0dafb8e1405