catkin should support the python setup.py argument py_modules

[wjwwood]

When using this argument to setup.py's setup() function catkin warns:

*** Arguments ['py_modules'] to setup() not supported in catkin devel space in setup.py of camera_info_manager_py

It ges installed into the install space, but it does not create a redirection placeholder for the devel space.

Since this is a core functionality of python's distribution system we should support it.

Here is an example setup.py:

from distutils.core import setup
from catkin_pkg.python_setup import generate_distutils_setup

d = generate_distutils_setup(
    py_modules=['camera_info_manager'],
    package_dir={'': 'src'}
)

setup(**d)