Add logging support in STPacketServer

This makes all of the messages from STPacketServer classes go through
the logging module, and adds a root logger in robot.py
Add logging support to TinyEnc

Use the logging module for TinyEnc output
Combine Packet and STPacket*

This combines the STSession, STPacketServer and Packet classes into a
single module called packetcomms. STSession and STPacketserver have also
been renamed to Session and Server respectively
Add documentation and copyright header to packetcomms