Having a separate Weekday checkbox

[FritzHerbers]

Would be nice to have a separate Weekday checkbox to wizard like produce the following:
0 0 0 1W 1/1 ? *: on the first weekday of the month
0 0 0 14W 1/1 ? *: on the weekday nearest day 14 of the month (missing)
0 0 0 LW 1/1 ? *: on the last weekday of the month

Proposal:

In Montly having "On the":
First (without "Weekday")
1
..
31
Last (without "Weekday")

Additional checkbox for Weekday modifier ("W")

[vincentjames501]

Open to pull requests here.