flash_test now calls only spi_setup instead of swift_nap_setup
Adding shebang to m25 flashing script.
Don't process messages with CRC errors.
Attempt to clear RX buffer at startup in serial_link.py

Better but doesn't always work. Needs more attention.
Updates/fixes to debug_send_message.

Now has return value indicating if the message was sent or not.

Only sends message if there is room in the TX buffer for all USARTs it is supposed to be sent on.
Cleaning up m25_flash code.

Now uses debug_send_message return code to block until msg sent successfully.

Cleaned up coding style a bit.

Increased read transfer size to 192 bytes for increased speed / efficiency.