Add reference page to documentation using Sphinx autodoc (#312)

* Docstrings and type annotations for almost every method
* New /reference API documentation page using Sphink autodoc
* Custom Read The Docs config, to get autodoc working
* Fix for #313 (add_foreign_keys() doesn't reject being called with a View)
* Fixed #315 (.delete_where() returns [] when it should return self)

docs/reference.rst

@@ -0,0 +1,69 @@
+===============
+ API Reference
+===============
+
+.. contents:: :local:
+
+.. _reference_db_database:
+
+sqlite_utils.db.Database
+========================
+
+.. autoclass:: sqlite_utils.db.Database
+    :members:
+    :undoc-members:
+    :show-inheritance:
+    :special-members: __getitem__
+    :exclude-members: use_counts_table, execute_returning_dicts, resolve_foreign_keys
+
+.. _reference_db_queryable:
+
+sqlite_utils.db.Queryable
+=========================
+
+:ref:`Table <reference_db_table>` and :ref:`View <reference_db_view>` are  both subclasses of ``Queryable``, providing access to the following methods:
+
+.. autoclass:: sqlite_utils.db.Queryable
+    :members:
+    :undoc-members:
+    :exclude-members: execute_count
+
+.. _reference_db_table:
+
+sqlite_utils.db.Table
+=====================
+
+.. autoclass:: sqlite_utils.db.Table
+    :members:
+    :undoc-members:
+    :show-inheritance:
+    :exclude-members: guess_foreign_column, value_or_default, build_insert_queries_and_params, insert_chunk, add_missing_columns
+
+.. _reference_db_view:
+
+sqlite_utils.db.View
+====================
+
+.. autoclass:: sqlite_utils.db.View
+    :members:
+    :undoc-members:
+    :show-inheritance:
+
+.. _reference_db_other:
+
+Other
+=====
+
+.. _reference_db_other_column:
+
+sqlite_utils.db.Column
+----------------------
+
+.. autoclass:: sqlite_utils.db.Column
+
+.. _reference_db_other_column_details:
+
+sqlite_utils.db.ColumnDetails
+-----------------------------
+
+.. autoclass:: sqlite_utils.db.ColumnDetails