Suggestion: Configuration Jumpers

[milesfrain]

For future HW revisions, it would be great to have easy configuration with 0.1" pitch jumpers on the following:

• GS1 for termination (and / or the switch footprint suggestion in Modify board to add placeholder for smd dip switch and termination resistor #1)
• Breaking CAN_TX and CAN_RX so the board can be re-purposed as a simple transceiver breakout for testing CAN on other micros (e.g. without using the included STM32 and USB).

To keep manufacturing simple and not add to the BOM, just the through-hole footprints could be added for users to populate themselves if they wish. In the case of the CAN_TX and CAN_RX interruption, we can score the trace to break the existing connection.