Declutter examples

[pelesh]

Create ExampleHelper class to encapsulate some common functions used in Re::Solve examples, so that examples are less cluttered and more informative.

Some outstanding items before this draft is ready for review:

• Expand functionality in gpuRefactor.cpp so that the example can use CUDA SDK and ROCm solvers.
• Implement sysRefactor.cpp example using ExampleHelper class.
• Implement GMRES example(s) using ExampleHelper class.
• Implement kluRefactor.cpp for refactorization with iterative refinement on CPU.
• Instrument examples for performance profiling.