refs #9428. Fix errors and tests.

Error in IntegratePeaksUsingClusters test introduced (previously) and now fixed.
Windows disambiguation of exact enum to use.
refs #9428. Swap in PeakClusterProjection into integration.

refactoring step. Common code usage.
refs #9428. More tests and performance tests.

Increase test coverage. Add performance tests, and refactor the implementation a little.