Move some heart tests into subfolders.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20331 b5f69653-2bf5-0310-8201-b0dafb8e1405
Fix #2442.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20332 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2446 - remove very old failing test (see r3281 for the history!)

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20333 b5f69653-2bf5-0310-8201-b0dafb8e1405
One missed in r20331.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@20334 b5f69653-2bf5-0310-8201-b0dafb8e1405