Sphinx-csharp

* Use _() instead of l_() function, which will be removed in Sphinx 3
* Drop support for Sphinx 1.4 and 1.5 as they don't support _() correctly

* Added inherits directive (5)
* Drop support for Python 2.6
* Add support for Python 3.6 and 3.7

* Allow default values in method signatures to contain brackets

* Support Sphinx >= 1.3
* Fix future deprecation in Sphinx 1.7
* Make code pep8 and pylint conformant

* Add support for parameter modifiers and indexers

* Add namespace directive