With the VBUS symbol merged into the KiCad library, I no longer need to
use my own.  This commit changes the schematic to use the standard VBUS
symbol rather than a custom one.

The SOT-89 footprint changed its name slightly in the KiCad library,
so the voltage regulator has been updated accordingly.  It has a nice
new 3D model too.  It's not weird and blue anymore.  I like it.

The SOD-123 was also updated to have a 3D model.  The board now only
lacks models for the footprints I made myself.  Heh.

That library is getting less important though, thankfully.  Still, while
it has symbols we need, it should be accessible.

In preparation for adding a second board (the programming jig) to this
repository, I've moved the PD Buddy Sink files to their own directory.