Refactoring for mesh initialization and unit tests

- refactored a few for cycles in EntityInitializer to use ParallelFor
- modified function findEntitySeedIndex in Initializer to use find instead of insert
- modified FPMAReaderTest to use slightly bigger mesh for testing
- added a few explanatory comments
- deleted unused methods from SubentitySeedsCreator
- created specialization of Formatter in Assert.h for std::pair to avoid compilation error caused by calling inplaceExclusiveScan on array of pairs