Some TODOs

[smattheis]

• Revise submit/stream.py to use Python sockets instead of netcat (similar to submit/batch.py).
• Change Calendar.getInstance().getTimeInMillis() to System.currentTimeMillis() in TemporaryMemory.
• Add a tracker.properties option to bound MatcherKState.
• Consider reuse of client connections in AbstractServer especially for the use with the TrackerServer, i.e., keep connection open (repeated REQ-RESP pattern) and handle connections closed from client side (also needed for downwards compatibility).