pyapi DOC basic documentation via sphinx

integrate python docs build in our cmake build system via pyapidoc target.
diff --git a/python/docs/api.rst b/python/docs/api.rst
new file mode 100644
index 0000000..f8a400b
--- /dev/null
+++ b/python/docs/api.rst
@@ -0,0 +1,6 @@
+API documentation
+*****************
+
+.. automodule:: netconf2
+     :members:
+