Rtbkit 480

This adds basically two things:

  * support for a lightweight C++ library to write a bidder (rtbkit/lwrtb)
    this is consistent with the simplification effort started in RTBKIT-455. As an example, example/lw_bidder.cc. The only thing which a hurried customer needs to have i/o develop an agent, instantiate an RTBKIT::lwrtb::Bidder and implement callbacks further used. 

  * support for SWIG, along with a bidding agent 
    - as light example example/bidder.py. 

In order to build:
  * make sure swig in installed 
  * export BIN=$PATH/rtbkit/build/x86_84/bin     # or wherever
  * make compile PYTHON_ENABLED=1          # or edit jml-build/arch/x86_84.mk