Changes to the USBUART to make it less likely to drop characters at higher baud rates.

USB UART seems to work fine at 115.2Kbps or 230.4Kbps, but starts to drop characters
as the data rate goes higher. This commit changes the usbuart ISR to fill a software
FIFO, and adds a low priority timer interrupt to run deferred processing to drain a
FIFO and send USB CDCACM packets, rather than calling the usb send within the UART
ISR.

Tested on native platform, up to 1.5MBps.
usbuart: Fix build error and clean up whitespace.
Added new contrib hardware folder including README
Added EAGLE temporary files to .gitignore
Added blank parts list
Majority of Components in place
Major components added to parts list
Added LEDs
Attempt to fix table
Schematic provisionally complete
Completed board layout
Completed parts list
Fixed final list of parts list
Added links to parts list
Changed text on the end of the board to "ARM Cortex Debug"
Added switch on BOOT0
Wrote README text
Fixed up README
Added image to README
Fixed image in README