Document IMRU collaboration/data flow

need to document IMRU components interaction.
perhaps small wiki with collaboration and data flow diagrams.

IMRU main flow fairly obvious, but following things required some debugging/reverse engineering:

• input data is not used unless constructor of MapFunction defines it as parameter
• how to configure input data set
• Update function returns iEnumerable of results as generic case. it's up to algorithm to decide which result should be included into the list: it can decide include result from last iteration only
• Map input/output codecs are required in order to serialize/deserialize data across nodes.
• Optional Map input/output data converters can be used by algorithm developer to improve performance of distributed calculations. For instance send subset of dimensions to a node.