Added bare bones stm32 config.

Driver requires implementation in fnet_stm32_mac.c/h,
 copied from Freescale fnet_fec.c/h.
TODO: Implement init, input, output, then test.
Using LWIP as the model for integration in ChibiOS and fnet_fec as the model
for FNET integration.
Example LPC driver.
Fleshed out chibios ethernet driver in fnet_stm32_eth.c/h.
Todo: tx/rx descriptors.

Added fapp.c to SRCs and fnet_demos/common/fnet_application to include dirs.
Exclude stm32_mac.c/h. Do not track html docs in git tree.
fnet_stm32_eth.c: Mostly ported. TODO: Chibi to FNET descriptors in I/O funcs.
fnet_stm32_serial.c: Ported. Untested.
fnet_chibios.c: Added FNET_CFG_OS_EVENT section. TODO: Test the CMSIS ISR mech
TODO: IRQ ISR stuff in fnet_stm32.c. Stubs there now. Might be better in
OS-specific code side.