The injection time was getting incremented once when it shouldn't
have been and didn't give any information on the actual time
step that particles were injected at (instead it was just a counter
telling how many times before particles were injected). Also, there
wasn't any good mechanism to figure out the actual simulation time
for ParticlePaths so I added in functionality in the base class to
add in extra arrays specific to a concrete flow path algorithm. This
was then used to add in Simulation Time for particle paths.

Change-Id: Idaaff28439ff2b4c966ec02b871243c1e04e24b3