[Docs] Reorganise and add sections from wiki

- Change the layout and contents of docs to be better organised and
  follow ideas from: https://www.divio.com/blog/documentation/
- Use markdown for non-technical documents to speed up writing.
- Added new sections and imported documents from Trac wiki.

Build fixes:

- Added a patch to fix recommonmark 0.4 and doc referencing:
    https://github.com/rtfd/recommonmark/issues/93
- Set docs build in tox to Py2.7 since there are problems with autodoc
  mocking multiple inheritance on Python 3 resulting in metaclass errors.
- Supressed warning about `modules.rst` not in the toctree by creating
  a static `modules.rst` with `:orphan:` file directive and add to git.
  Also skip creating this toc file with sphinx-apidoc in setup and tox.
- Simplified finding exported RPC and JSON API methods by adding an
  autodoc custom class directive. Removed unneeded __rpcapi.py.

docs/source/devguide/how-to/index.md

@@ -0,0 +1,8 @@
+# How-to guides
+
+This is a collection of guides for specific issues or cover more details than
+the tutorials.
+
+## Web JSON-RPC
+
+- [Connect to JSON-RPC using curl](curl-jsonrpc.md)