Scan the network to discover the Dynamixels present.
This function builds an internal list of Dynamixels present on the network.
NOTE: Typically call this function only once per DynamixelNetwork instance
since it will rebuild the list and create new Dynamixel instances to fill it,
orphaning any previously retrieved Dynamixels.
Scanning for all possible IDs (0 thru 254) can be time consuming.
So if the range can be constrained to predetermined values it can speed up the process.