Draft: Add sphinx documentation

The mechanism for building docs was copied from EveryBeam; it parses both Doxygen documentation and python documentation into a sphinx page.

doc/build-instructions.rst

@@ -6,8 +6,8 @@ Build instructions
 Radler can be installed as a stand-alone package, but is also installed as a part of `WSClean <https://wsclean.readthedocs.io>`_. 
 If you only want to install WSClean, it is not necessary to build Radler yourself.
 
-Dependencies:
-~~~~~~~~~~~~~
+Dependencies
+~~~~~~~~~~~~
 Radler needs a number of dependencies in order to successfully compile. On a clean (ubuntu 22.04) system,
 the dependencies can be installed with (see also the ``docker`` directory):
 
@@ -35,8 +35,8 @@ In order to be able to build the documentation with ``make doc``, ``sphinx`` and
 
 
 
-Quick installation guide:
-~~~~~~~~~~~~~~~~~~~~~~~~~
+Quick installation guide
+~~~~~~~~~~~~~~~~~~~~~~~~
 
 ::
 
@@ -47,8 +47,8 @@ Quick installation guide:
     make install
 
 
-Installation options:
-~~~~~~~~~~~~~~~~~~~~~
+Installation options
+~~~~~~~~~~~~~~~~~~~~
 
 (Use :code:`ccmake` or :code:`cmake -i` to configure all options.)