#2565 PETSc 3.5 support

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@22721 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2300 Fix coverage of several methods `AbstractAcinarUnitFactory`

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@22722 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2477 Make Swan units consistent with `VentilationProblem` (Pa and mm)

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@22725 b5f69653-2bf5-0310-8201-b0dafb8e1405