docs: generate deltachat-rpc-client documentation

To preview the docs, run:
```
scripts/build-python-docs.sh
firefox dist/html/index.html
```

I have removed the Makefile because modern Sphinx Makefile is just a
wrapper for `sphinx-build -M`:
3596590317/sphinx/templates/quickstart/Makefile.new_t
and sphinx-quickstart even has an option `--no-makefile`.
`make.bat` makes even less sense.
In `scripts/build-python-docs.sh` I use `sphinx-build` directly
without `make` wrapper.

python/doc/cffi/examples.rst

@@ -0,0 +1,59 @@
+Examples
+========
+
+Once you have :doc:`installed deltachat bindings <install>`
+you need email/password credentials for an IMAP/SMTP account.
+Delta Chat developers and the CI system use a special URL to create
+temporary email accounts on `testrun.org <https://testrun.org/>`_ for testing.
+
+Receiving a Chat message from the command line
+----------------------------------------------
+
+Here is a simple bot that:
+
+- receives a message and sends back ("echoes") a message
+
+- terminates the bot if the message `/quit` is sent
+
+.. include:: ../../examples/echo_and_quit.py
+    :literal:
+
+With this file in your working directory you can run the bot
+by specifying a database path, an email address and password of
+a SMTP-IMAP account::
+
+    $ cd examples
+    $ python echo_and_quit.py /tmp/db --email ADDRESS --password PASSWORD
+
+While this process is running you can start sending chat messages
+to `ADDRESS`.
+
+Track member additions and removals in a group
+----------------------------------------------
+
+Here is a simple bot that:
+
+- echoes messages sent to it
+
+- tracks if configuration completed
+
+- tracks member additions and removals for all chat groups
+
+.. include:: ../../examples/group_tracking.py
+    :literal:
+
+With this file in your working directory you can run the bot
+by specifying a database path, an email address and password of
+a SMTP-IMAP account::
+
+    python group_tracking.py --email ADDRESS --password PASSWORD /tmp/db
+
+When this process is running you can start sending chat messages
+to `ADDRESS`.
+
+Writing bots for real
+-------------------------
+
+The `deltabot repository <https://github.com/deltachat/deltabot#deltachat-example-bot>`_
+contains a little framework for writing deltachat bots in Python.
+