- made some processed command line settings available to plugins

- General.Exit() method for plugins to close Doom Builder
- command-line parameter -delaywindow to keep the main window hidden until nothing more to process. This gives plugins the ability to perform an operation without showing the main window at all if the plugin calls General.Exit() before the window is shown. Usefull for batch processes in which no interface window is desired.
- some new plugin events that occur before and after making a new map and opening a map.