TOS name insconsistencies

[davidcc73]

I already fixed those at my fork: https://github.com/davidcc73/P4-SFC

but the project is already too different to merge, the changes were:

For the P4 code and its .json files with table entries, TOS was just the 6 LMS bits of TOS, which is DSCP, while the remaining 2 bits were correctly assigned as ECN. So in the P4 code, the TOS field was changed to what the field actually is, the DSCP field.

For Python, the send.py demanded a TOS value to use in the packets, and by doing that, it manipulated the DSCP, but the ECN filed too, which is used to do congestion control at run time, so it was changed to ask for just for the DSCP value, and only inject that part in the created packet.