Add a StaticMeshComponent to an Actor

Any code you can have in a .cpp file you can have in a .h file. You could declare and define every function of a class in the .h file if you wanted to. It will increase your compile time dramatically though if you add all your code to .h files as it will have to parse that code for every other file that includes the header. However, the compiler tends to have an easier time inlining functions that are written in the header.