Insteon: Move update_flags, Condense KeypadLinc Classes, Add I2 Support to update_flags

- Update flags belongs in the Keypadlinc class as it only works on these devices
- Condensed the set routine from Keypadlinc and KeypadlincRelay into Keypadlinc
- Added I2 support to update_flags
- - In order to support the old version of update_flags, the manner in which the routine works is a little odd as users have to pass a hexadecimal flag to the routine.  This could obviously be changed or supplemented in the future.