Fixes numerous issues for benchmarking (#93)

* Fixes numerous issues for benchmarking

* Batch size was used in place of number of iterations per batch size when averaging batch size results.
* C++ benchmarking was developed on top of CallableFunc, which was designed for devices where multiple input sets were not needed. C++ benchmarking on the CPU, at least, needs these multiple input sets. This change fixes this issue.
* Number of iterations per batch was added as a command line argument
* CallableFunc instances for devices that need cache flushing will have extra data generated for them