PC updates

[PaulZC]

Many updates / corrections:

• Add Mag Jack, KSZ8041NLI, mosaic-T, 74LVC2T45DC dual buffer / level-shifter, 10-way screw cage terminal
• Add existing R's, C's from Eagle
• Add existing DC-DC converters from Eagle (REC15E, Ag9900M)
• Correct the SMA Edge footprints: all now use Pin 1 for "In", and Pin 2 for "Ext" (GND). Same as u.FL.
• Add YGR triple CBI LED
• Add new components: SiT5358, 130nH inductor
• Allow bridged solder mask on jumpers
• Add missing courtyard to Panasonic_D
• Move SOT-323 Ref from User.1 to F.Fab (keeping User.1 free for "Milling")

Note: the DC-DC converter footprints are in Semiconductor-Standard. They probably need a new home of their own? Not Electromechanical. Something new?

[nseidle]

I moved the DC-DC and PoE modules to Semiconductor-Nonstandard.

The VSSOP-8 makes me a bit nervous. I was working on a VSSOP as well and used one of the built-in KiCad packages. Because it seems VSSOP can vary, I'd like to get some dimensions on that footprint name (3.1x2.9mm-P0.55 or whatever).

I've added a handful of commits for nits. Otherwise, looks great! Merging.