Modularize

Create real nxdtest module, so that things could be imported from there.
As the result switch `nxdtest` program from scripts to entry_point.

setup.py

 # nxdtest | pythonic package setup
-from setuptools import setup
+from setuptools import setup, find_packages
 
 setup(
     name        = 'nxdtest',
@@ -12,10 +12,10 @@ setup(
 
     keywords    = 'Nexedi testing infrastructure tool tox',
 
-    packages    = [],
+    packages    = find_packages(),
     install_requires = ['erp5.util', 'six'],
 
-    scripts     = ['nxdtest'],
+    entry_points= {'console_scripts': ['nxdtest = nxdtest:main']},
 
     classifiers = [_.strip() for _ in """\
         Development Status :: 3 - Alpha