The previous version of BenchmarkInSitu added arguments to its argv list
by using `strdup`. However, this method will leak memory, which is not
great. Replace this with a safer mechanism that will properly delete
memory at the end of the program (and satisfy any memory analyzers).
This also fixes a warning from MS about `strdup` being deprecated.
Previous version had a hard-coded loop for updating the dataset. This change relenquishes control over to google benchmarks. Running it from the command-line will iterate each sub-benchmark a different number of iterations depending on how long each individual test takes. The number of iterations can be increased (but not controlled) by increasing the minimum time for each test. Alternatively, using the "repetitions" argument, you can control exactly how many times the benchamrks are run.
See the README for InSitu that throughly documents the arguments.
The enumerations in `vtkm::cont::Field::Association` were renamed in the
previous commit. The old names still exist, but are deprecated. Change
the rest of the code to use the new names.
