Proposal for extension of generic_can

This proposal is because Ini-config files are deprecated. In this proposal there is not importat which middle-ware is used since the configuration parameters are given during object creation. In my case is used inside ROS, but think is better when doesn't depend on any ROS-specific code (like ROS-parameters).

Tested and used is only PCAN-USB dongle, I don't have possibiliy to test for other CAN interfaces, so empty functions are in other CAN implementations.

Also some constants are added to CanItf.h file to make configuring easier.

**It is tested under indigo, but should also work under hydro.**