Improve bsbport flash and memory usage

- remove float
- add const where possible
- fix some wrong formated lines
- invert bytes on tcp connection also
- tcp connection now uses same send buffer and send_start  
- fix bsbport_rx_periodic() sometimes to drops a message because lenght byte was not received already
Please check if this produces the same result with less flash usage.
*(int16_t*)&data[1] = tmp;