docs: Update a couple of references and titles

docs/api/backends.rst

@@ -1,12 +1,12 @@
-.. _backend-provider-api:
+.. _backend-api:
 
-********************
-Backend provider API
-********************
+***********
+Backend API
+***********
 
-The backend provider API is the interface that must be implemented when you
-create a backend. If you are working on a frontend and need to access the
-backend, see the :ref:`backend-controller-api`.
+The backend API is the interface that must be implemented when you create a
+backend. If you are working on a frontend and need to access the backend, see
+the :ref:`core-api`.
 
 
 Playback provider
@@ -30,8 +30,8 @@ Library provider
     :members:
 
 
-Backend provider implementations
-================================
+Backend implementations
+=======================
 
 * :mod:`mopidy.backends.dummy`
 * :mod:`mopidy.backends.spotify`

docs/api/concepts.rst

@@ -1,4 +1,4 @@
-.. _backend-concepts:
+.. _concepts:
 
 **********************************************
 The backend, controller, and provider concepts
@@ -12,11 +12,11 @@ Controllers:
     functionality. Most, but not all, controllers delegates some work to one or
     more providers. The controllers are responsible for choosing the right
     provider for any given task based upon i.e. the track's URI. See
-    :ref:`backend-controller-api` for more details.
+    :ref:`core-api` for more details.
 Providers:
     Anything specific to i.e. Spotify integration or local storage is contained
     in the providers. To integrate with new music sources, you just add new
-    providers. See :ref:`backend-provider-api` for more details.
+    providers. See :ref:`backend-api` for more details.
 
 .. digraph:: backend_relations
 

docs/api/core.rst

@@ -1,4 +1,4 @@
-.. _backend-controller-api:
+.. _core-api:
 
 ********
 Core API
@@ -9,8 +9,6 @@ The core API is the interface that is used by frontends like
 :mod:`mopidy.frontends.mpd`. The core layer is inbetween the frontends and the
 backends.
 
-If you want to implement your own backend, see the :ref:`backend-provider-api`.
-
 
 Playback controller
 ===================

docs/changes.rst

@@ -616,9 +616,9 @@ to this problem.
     :class:`mopidy.models.Album`, and :class:`mopidy.models.Track`.
 
   - Prepare for multi-backend support (see :issue:`40`) by introducing the
-    :ref:`provider concept <backend-concepts>`. Split the backend API into a
-    :ref:`backend controller API <backend-controller-api>` (for frontend use)
-    and a :ref:`backend provider API <backend-provider-api>` (for backend
+    :ref:`provider concept <concepts>`. Split the backend API into a
+    :ref:`backend controller API <core-api>` (for frontend use)
+    and a :ref:`backend provider API <backend-api>` (for backend
     implementation use), which includes the following changes:
 
     - Rename ``BaseBackend`` to :class:`mopidy.backends.base.Backend`.