Utils.SkyFit2: add reference lenses option when building new platepar

[adalava]

This tries to make much easier to build a new platepar when station uses the most common lenses: 4mm and 6mm M16 mount. Reference data was taken from BR000F and BR0001.

This seems to work to me. Please check if this change is useful and if I'm missing something.

More tests are welcome. :)