InsteonPLM: better support for Keypad Buttons and various fixes:

This pull request improves functionality for several keypad devices and removes duplicate state updates.

1) Prettier logging of modem link database content
2) ability to set maximum dimmer level via parameter in binding string
3) added "group" parameter as binding configuration which allows to control keypad buttons from openhab
4) fixed buggy X10-style address printout for Insteon Address when logging group addresses.
5) eliminated duplicate events published to openhab bus due to polling and duplicate ALL LINK messages