RealFloat Zero Padded Exponent

Some dxf files have doubles encoded in scientific notation with the exponent padded with zeros.

https://github.com/LibreCAD/LibreCAD/blob/8e10245994d8307a76cedc3cbffe471de88c8325/librecad/support/library/algoritm/alg27.dxf#L1560

I suggest adding a Bool to FGeneric and FScientific to allow for padding the exponent with zeros to the maximum precision of the exponent.

Start by locating the FGeneric and FScientific definitions and reviewing how they format exponents. Compare their behavior with the linked LibreCAD DXF example, then determine how zero padding to the maximum exponent precision should be exposed and tested.

Written by the indexing model from the issue text.