Allow negative values in the `flags` field of things.
The slope vertex thing has the ability to use an absolute Z value by putting any non-zero number in the parameter field, which is quite useful. However, Zone Builder cannot properly represent negative values in the Flags
field, forcing users to wrap the value by hand for any slopes that dip below 0. I would suggest that the flags value somehow be allowed to receive and display both signed and unsigned values, just like the Angle
field.