Editor enhancements

** It would be nice if there was a way to selectively hide BSP brushes by type. For example, hide solid BSPs or hide semi-solid BSPs. This was a standard feature in most of the earlier brush-based editors and was very handy when optimizing a level.

** There seems to be dozens of commands in the editor that are inaccessible unless you bind a key to them. They really need to be added to a tool menu.

** It would be nice if you could change the colors of the background and objects in the orthographic views. Some of the colors are very difficult to see against the dark grey background currently in use.