Stability improvements and API refactor

1. Cross entropy benchmarks have helped us debug QUnit to its most stable, accurate, and performant point to date.
2. Builds have been tested on Linux, Windows, Apple, and with VC4CL on the Raspberry Pi 3.
3. QFusion was determined to be obsolete, including for performance considerations, and it was removed.
4. The "Hash" method has been added, which effectively lets the user specify any one-to-one function (without phase effects) for unitary qubit state transformation via a classical hash table.
5. CMake options now include arbitrary (power-of-two) maximum qubit capacity in a single QUnit, with the Boost libraries for big integers. Of course, allocation is still limited by system resources, and the maximum OpenCL "shard" indexing is 64 qubits or less, (which is safely outside of possible resource limits for "Schrödinger method" simulation).
6. Documentation has been brought into line with the features and benchmarks of the new release.