add rudimentary client request handler module

* add client (AMF) request handling module (stub implementation)
* move persistence, RPC and GSJS initialization to worker process
  (master process now really just fulfills cluster master role)
* some unrelated cleanup in server.js
add npm package "amflib"
add AMF (de)serialization benchmarks
add AMF message processing to Session class

* deserialization of incoming AMF data
* call request processing function for each message, wrapped in a
  request context
* rudimentary request error handling
* adjust existing tests, add unit tests for new functionality
turn requestContext module into a class

* it seems more appropriate to have a RequestContext class where one
  instance is created for each request and attached to the respective
  Fiber, than a singleton module which sticks all those properties onto
  the Fiber
* nearly all changes in this commit apart from RequestContext itself
  are merely adjustments to changed names and slightly different
  instantiation/"run" function call semantics
add request and session information to log messages

* move logging initialization to dedicated module
* add a transparent wrapper for all log calls to include request
  context and session information when available
* removed dedicated child logger from Session class (no longer needed)
Merge pull request #4 from yelworc/req-processing

client (AMF) request processing