#2404 - make use of `NodeVelocityWriter`, move `mOutputNodeVelocities` to cell population

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19359 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2404 - doh, replace file

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19360 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2404 - sigh....

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19361 b5f69653-2bf5-0310-8201-b0dafb8e1405
Note that `ChasteSyscalls.hpp` includes `<sys/stat.h>` in a cross-platform-friendly way.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19362 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2404 - fix nightly test

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19365 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2370 add an example of using a contraction cell factory for heterogeneous contraction models.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@19366 b5f69653-2bf5-0310-8201-b0dafb8e1405