Add configuration of serial protocol settings (25-serial node)

- Add support for configuration of protocol parameters (data bits,
parity, stop bits)
- Set serial device/port using select list (discovered ports)
- Provide default settings for existing flows that do not yet have
serial protocol settings


The GUI screen for defining the serial configuration has a few additional fields to set the data bits, parity and stop bits, and the port selection has been changed into a pick list from available ports

![screen shot 2014-04-21 at 23 24 25](https://cloud.githubusercontent.com/assets/1499454/2759328/aa6e6994-c99e-11e3-85c7-d7d3d13561c7.png)