can control multiple HUD elements

returns: ID to the newly create HUD state

Typical usage (hiding the minimap):

   -- Create a new HUD display state, add the minimap element to be hidden, and apply the state
   local my_hud_state = hud_display_create_state()
   hud_display_set_element(my_hud_state, HUD_ELEM_MINIMAP)
   hud_display_commit_state(my_hud_state)