upd-fix: fixing connection bugs in htmlboard

- fix: fixed client centric callback, to reduce the number of callback.
- upd: change the python bridge command line arguments and the call from
the board.
- upd: improve the python bridge with dynamic array for the pin layout.
- fix: fixed server centric htmlboard read function to work with the new
client connections.
- add: firmata_spi.hex.
- add: changelog.txt