Add USB-Mini-AB-Molex-56579-0519

This is my very first foot print in KiCad but I tried to follow the KLC! This adds the footprint for this USB Molex connector according to this drawing. It required a little quirk to make the solder mask on the top: since this device is soldered from the bottom only there should not be a pad on the top copper layer. However, when there is none then the solder mask will happily cover the drill holes. To work around this I have added SMD pads to F.mask that matchs exactly the drill holes of all the THT pads that comprise the plated holes and the back side pads.

The only thing were I deliberately violate the KLC is the keepout area... drawing hachures manually is just stupid.