Library tweaks (non-structural)

I've adjusted the library as follows:
Changed text alignment (centered, mostly) on parts, made positioning
more consistent.
Reduced tKeepout as it was a rather on the generous side for the 0402
and 0403 parts.
Added / fixed a few Device descriptions.
Board clean-up, parts updated from modified library

Schematic:
- Only updated parts from the modified library
Board:
- Moved parts, vias, onto mm grid (was arbitrary?)
- Major re-tracing to keep traces on-grid
- Added full board ground planes (both sides) with grounding vias
scattered around - edges are now fully grounded.
- Moved some parts around beyond grid, e.g. C6 closer to VCCio
- Added 'INFNOISE TRNG' to tNames
Notes:
- Passes ERC and DRC (based on originally included OSHpark Design
Rules), with the exception of the slot pads for the USB connector
(originally approved).