This allows the path for the default filter to be specified explicitly
when creating a stream and reduces the need to rely on the default path
function to magically supply the path.
The default path function is now only used if, when a filter is added to
a stream, it has neither a path nor a path function already.
Adapted the existing Log::create_stream calls to explicitly specify a
path value.
Addresses BIT-1324
- There are still some broken events in the modbus analyzer because
I don't have traffic to test with (coil and record related events primarily).
- There are a few example scripts in policy/protocols/modbus
