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.

src/DataTransfer.cpp

@@ -10,7 +10,7 @@
 namespace executor_cases {
   
   void Mov_rm32_r32(CPUContext& cc) {
-    x86::ModRM modrm = cc.m_Instruction.optional.m_ModRM;
+    x86::ModRM modrm = cc.m_Instruction.m_ModRM;
 
     std::cout << "[Instruction] ";