#6 Make Python module of FDNT

The Python interface is working, and I need to wrap up this issue.  This pull request is to remind myself what has been done.

Major changes:
 * scons compilation (easy to deal with compiler differences of different systems)
 * Python / C++ interface with Boost Python
   * `position.py` module: `PositionD` and `PositionI` class
   * `bounds.py` module: 
   * `fdntimage.py` module: `FDNTImage` class (along with `FDNTImageS`, `FDNTImageI`, `FDNTImageF`, `FDNTImageD`)
   * `runfndt.py` module: `FDNTShapeData` class contains the shape measurement results, `RunFDNT()` function
 * A sample Python script: examples/demo1.py 

Sadly, I will be reviewing my own code for now.
`default_cxx` has now replaced `g++` in default setting line.