ECNSpider should generate observations, not flow data

[britram]

ECNSpider currently generates one row of output per flow; instead, it should generate one row of output per path, with an additional key "condition". Conditions should include:

• ECN not negotiated but ECT/CE mark observed
• ECN negotiated, ECN mark observed, and potential real CE mark observer
• ECN negotiated and ECN mark observed (SEW->SAE + ECT[0,1])
• ECN negotiated but no ECN mark observed (SEW->SAE)
• ECN not negotiated (SEW -> SA)
• ECN connection failed (SEW -> X, while S -> SA)
• Target Down (SEW -> X, S -> X)

Actually, let's do it this way: an observation can have multiple conditions. The following potential conditions are exclusive.

• Target Down (no connections work) vs ECN-dependent connectivity (ECN fails) vs ECN-independent connectivity (connection state same) vs possibly-transient connectivity (non-ECN fails)
• ECN negotiated vs ECN not negotiated
• ECT0 mark seen post-negotiation vs ECT0 mark seen pre-negotiation vs ECT0 mark not seen
• ECT1 mark seen post-negotiation vs ECT0 mark seen pre-negotiation vs ECT1 mark not seen
• CE mark seen post-negotiation vs CE mark seen pre-negotiation vs CE mark not seen

[britram]

In more detail, the fields of the JSON document should be as follows:

{
  time:
  sip:
  dip:
  condition: [ (some encoding of the list in the previous comment) ]
  hostname: (www.xxx.yyy, if relevant)
  rank: (from the alexa list, if relevant)
  flow_results: [
    {
      ecnstate: True,
      sp:, dp:, ect0,: ect1:, ce:, other flags...
    },
    {
      ecnstate: False,
      sp:, dp:, ect0,: ect1:, ce:, other flags...
    },
  ]
}

[britram]

This should happen after the standalone-observer, multiprocessing-observer, and mpo-all-results branches merge back to master.

[gubser]

also look at mami-project/pto-core#16