Add definition for SSOP-20_4.4x6.5mm_P0.65mm (existing, but not generated)

The adds a generator for the existing SSOP-20 4.4x6.5 P0.65mm package.

Datasheet:

http://www.nxp.com/docs/en/data-sheet/PCF8574_PCF8574A.pdf

New top, old bottom:

Includes the JEDEC standard and "SOT226-1" as keywords.

The file is not well ordered, but I put it roughtly where it should be, so at least it's not making it worse.

Footprint MR: kicad-footprints!3657 (merged)