Add explanations

[kijungs]

We have to add comments for all public classes and public methods within the classes so that we are able to run javadoc to create an API documentation automatically.
Especially, we need detailed explanation for the following classes:

• ComputeTask
  (what are the steps done in ComputeTask and how ComputeTask uses group comm, considering finite state machine that describes Controller and Compute Task state changes)
• DataParser
  (how DataParser is working. There are two methods: parse and get. Why do you have two)
• Driver
  (main logic of the Driver)
• Stage
  (main logic of a Stage)
• UserJobInfo
• UserParameters
  (what are needed at Driver, and ControllerTask explicitly)
• KeyValueStore
  (how we use this key value store)
• UserComputeTask
  (iteration)
• Each Machine Learning Algorithm and its important parameters
• FlexionConfiguration
• FlexionParameters

[bchocho]

+1 I'd like to add to the list:

• ControllerTask
• UserControllerTask

[jsjason]

The neural network classes need documentation too. We also need READMEs and a few diagrams.