deprecate genapp.sh

this new script `build.py` deprecate `genapp.sh`, and is more convenient to use (search dependent libraries dynamically and copy them inside)

currently it supports darwin ( OS X ) platform and Xcode generator. however it is easy to extend to the other two platforms, i.e. windows (mingw) and linux.(I have write part support of them, such as `get_dependencies` function via parsing `ldd`'s output).

after all, it is written by python, more maintainable and convenient to play with.