Enable WDT during bootloader
Switch to single-pass compare and write; add api functions

Switch from "compare and validate then write" to "compare and
write".

Also add two helper functions:
__copy_tftp_flash: write the TFTP data from a given
                   W5100 UDP connection to flash then
		   reboot to the application
__copy_tcp_flash:  write the date from a given
                   W5100 TCP stream to flash then
		   reboot to the application