pyln: Split pylightning into multiple pyln modules

This is the first step to transition to a better organized python module
structure. Sadly we can't reuse the `pylightning` module as a namespace module
since having importable things in the top level of the namespace is not
allowed in any of the namespace variants [1], hence we just switch over to the
`pyln` namespace. The code the was under `lightning` will now be reachable
under `pyln.client` and we add the `pyln.proto` module for all the things that
are independent of talking to lightningd and can be used for protocol testing.

[1] https://packaging.python.org/guides/packaging-namespace-packages/

Signed-off-by: Christian Decker <decker.christian@gmail.com>

contrib/pyln-client/setup.py

@@ -0,0 +1,24 @@
+from setuptools import setup
+from pyln import client
+import io
+
+
+with io.open('README.md', encoding='utf-8') as f:
+    long_description = f.read()
+
+with io.open('requirements.txt', encoding='utf-8') as f:
+    requirements = [r for r in f.read().split('\n') if len(r)]
+
+setup(name='pyln-client',
+      version=client.__version__,
+      description='Client library for lightningd',
+      long_description=long_description,
+      long_description_content_type='text/markdown',
+      url='http://github.com/ElementsProject/lightning',
+      author='Christian Decker',
+      author_email='decker.christian@gmail.com',
+      license='MIT',
+      packages=['pyln.client'],
+      scripts=[],
+      zip_safe=True,
+      install_requires=requirements)