STEPS FOR CREATING A NEW COMPONENT:

1) add the struct to components.h
2) add the gui code to component_guis.h
3) add the code to call the gui function to properties_view.cpp
4) add the code to add a new instance of the component to selected entity in properties_view's ADD_COMPONENT popup (using PRESENT_COMP_CHOICE)
5) add serialize/deserialize code to entity.cpp