[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.

setup.cfg

@@ -24,7 +24,8 @@ known_third_party =
 # Ignore gtk modules, primarily for tox testing.
     pygtk, gtk, gobject, gtk.gdk, pango, cairo, pangocairo,
 # Ignore other module dependencies for pre-commit isort.
-    twisted, OpenSSL, pytest, recommonmark, chardet, pkg_resources, zope, mock
+    twisted, OpenSSL, pytest, recommonmark, chardet, pkg_resources, zope, mock,
+    sphinx
 known_first_party = msgfmt, deluge
 order_by_type = true
 not_skip = __init__.py