Add unit tests to simulator part 2

[CapdinCrando]

Follow up to #36 . Split this into two to go ahead and merge CMake build system, test structure, and bug fixes from part 1.

[CapdinCrando]

Files that still need unit tests (for now):

• [ ] api.cpp
• [ ] core.cpp
• [ ] system.cpp
• [x] replacementpolicy/firstinfirstout.cpp
• [x] replacementpolicy/lastinfirstout.cpp