P4 messages (which appear as HTTP post fields) Have the following
values:

app:  One of
test = "ecd://epls.coe.fsu.edu/P4test"
userControl = "ecd://epls.coe.fsu.edu/PhysicsPlayground/userControl"
linear = "ecd://epls.coe.fsu.edu/PhysicsPlayground/linear"
adaptive = "ecd://epls.coe.fsu.edu/PhysicsPlayground/adaptive"

uid:  User ID
context:  *Logon*, *Logoff* or current level.
sender:  "Physics Playground Client"
message: "Player Start", "Player Stop", "Get Statistics", "Get Next
Level" (redundant with URL).
timestamp: current time in ISO960 format (GMT time)
data:  Arbirary json object.

Player Start:
data sent <- empty list
data returned ->
   trophies:[ {level: coin},...],
   balance:value,
   spent:value,
   newPlayer:logical
   [this will be in LL messages, need ER to parse.]   

Player Stop:
data sent <- empty list
data returned -> empty list
  [Low priority, we will manually start/stop Dongle, EIP, EAP and
  ASP for this version.]

Get Statistics
data sent <- empty list
data returned ->
   [{statName:value},...]  -- EAP stats will give value between -1 and +1.
   [or possiblely]
   {statName:{High:prob1, Medium:prob2, Low:prob3}, ...}

Get Next Level:
data sent <- level completed, current topic
data returned <-
   {topic:currentTopic,
    levelsCompleted:[list of levels completed in topic],
    levelsToGo:[list of uncompleted levels in order],
    twitchMode:logical
    }