Define Files - enhancing function that creates a default screen 0

[bruceeaston]

Enhance ddefine's function that creates a default screen 0 so that  instead, it will prompt for a screen #/name, and a starting field #.  It can then run as it has (using the same functionality to determine how to fit as many fields on the screen as possible), except creating the specified screen #/name and respecting the starting field number.

Also, it should always prompt before overwriting any screen #/name.

This entire new functionality would better be place in define screens, where it can always be used without locking out other users.