Refactor: ModRM Handler replaced with compile-time lookup table.

Started refactoring to a library-based model to easily integrate
comprehensive unit testing. Added CPU exception handling system for
the GUI. Non-critical exceptions (though critical to execution of
emulated application) will not shutdown the application in the future
releases. Refactored Userspace::Run() logic so that the GUI-controls
reflect emulator behavior.

tests/CMakeLists.txt

@@ -0,0 +1,10 @@
+enable_testing()
+						
+add_executable(test test.cpp)
+
+target_link_libraries(test
+		      GTest::gtest_main
+		      )
+
+include(GoogleTest)
+gtest_discover_tests(test)