Fixed pin header 3d models. We had some of the models doubled up or not fully disabled. Now the TH pin headers are all using KiCad V5 3d model locations and are all disabled. This fixes #23

Improved silkscreen legend for more intutive usage.

Added USB signal pads. These pads can be used for testing, debugging as well as hard wiring a usb extension cable.

Added inline resistors on all PMOD connectors to allow for higher GPIO speeds.

Replaced 0402 4.7u capacitors with 0603 for consistency. Fixes #4

Fixed #6 Oscillator pinout and schematic symbol. Both bitsy and icebreaker.

Starting V0.2a of the icebreaker board.