Docstring update (#58)

* migrate docstrings from reST to google format

* add raises note

Also change behaviour of the `from_option` method to fallback to
disabled instead of raising exception on unknown option

* fix part of warnings for sphinx

* make identation a bit more readable

* review fixes

* add verbose description for properties to make them parsed by sphinx extenstion

* add demo sphinx generator

docs/source/ahriman.core.rst

@@ -0,0 +1,76 @@
+ahriman.core package
+====================
+
+Subpackages
+-----------
+
+.. toctree::
+   :maxdepth: 4
+
+   ahriman.core.alpm
+   ahriman.core.auth
+   ahriman.core.build_tools
+   ahriman.core.database
+   ahriman.core.formatters
+   ahriman.core.report
+   ahriman.core.repository
+   ahriman.core.sign
+   ahriman.core.status
+   ahriman.core.upload
+
+Submodules
+----------
+
+ahriman.core.configuration module
+---------------------------------
+
+.. automodule:: ahriman.core.configuration
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+   :private-members:
+
+ahriman.core.exceptions module
+------------------------------
+
+.. automodule:: ahriman.core.exceptions
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+   :private-members:
+
+ahriman.core.spawn module
+-------------------------
+
+.. automodule:: ahriman.core.spawn
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+   :private-members:
+
+ahriman.core.tree module
+------------------------
+
+.. automodule:: ahriman.core.tree
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+   :private-members:
+
+ahriman.core.util module
+------------------------
+
+.. automodule:: ahriman.core.util
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+   :private-members:
+
+Module contents
+---------------
+
+.. automodule:: ahriman.core
+   :members:
+   :no-undoc-members:
+   :show-inheritance:
+   :private-members: