updated test_cython_bug to use quantlib.ql for test on Windows
settings use quantlib.ql
fixing pxd for cashflow
preload the quantlib.ql in quantlib.__init__ to solve the flat namespace
resolution issue when loading dependent modules
migrated bonds.pyx to use quantlib.ql, moved low level version from settings to
ql module
missing cimport
updated setup.py to reflect usage of the new quantlib.ql module