Better integration with Google Benchmarks

Fixes: #463 (closed)

This MR attempts to integrate our benchmarks closer to Google Benchmarks, here is a list of the changes:

• You can directly pass any argument|option|--help to Google Benchmarks without the -- separator from any of the benchmarks binaries

• You can run compare.py using two different devices and filters with the help of the introduced script compare-benchmarks.py

• It adds Google Benchmarks compare.py script and its library files and removed deprecated benchCompare / benchSummary scripts

• It adds a README.md file in the benchmarking folder which explains:

• How to run benchmarks for VTK-m

• How to use filters

• How to compare benchmarks using two different devices and possibly options

• The README.md file is copied to the bin folder in the build folder when configuring cmake

Let me know if it would be better to splits commits for this MR.