docs: shuffle files to have the same logical hierarchy as on the generated doc

Also:
 - rename some files to remove redundant information from the filenames
 - rename many labels to match the filename and its place in the hierarchy
 - move lua_api under the scripting section

docs/rst/scripting/lua_api/lua_object_manager_api.rst

@@ -0,0 +1,104 @@
+ .. _lua_object_manager_api:
+
+Object Manager
+==============
+
+The ObjectManager (binding for :c:struct:`WpObjectManager`) provides a way to
+collect a set of objects and be notified when objects that fulfill a certain
+set of criteria are created or destroyed.
+
+To start an object manager, you first need to declare interest in a certain
+kind of object specifying a set of :ref:`Interests <lua_object_interest_api>`
+in the constructor and then you need to activate it by calling
+:func:`ObjectManager.activate`
+
+Upon activating an ObjectManager, any pre-existing objects that match the
+specified interests will immediately become available to get through
+:func:`ObjectManager.iterate` and the :c:struct:`WpObjectManager` "object-added"
+signal will be emitted for all of them.
+
+Constructors
+~~~~~~~~~~~~
+
+.. function:: ObjectManager(interest_list)
+
+   Constructs a new object manager.
+
+   Combines :c:func:`wp_object_manager_new` and
+   :c:func:`wp_object_manager_add_interest_full`
+
+   The argument needs to be a table that contains one or more
+   :ref:`Interest <lua_object_interest_api>` objects. The object manager
+   will then contain all objects that match any one of the supplied interests.
+
+   Example:
+
+   .. code-block:: lua
+
+      streams_om = ObjectManager {
+        -- match stream nodes
+        Interest {
+          type = "node",
+          Constraint { "media.class", "matches", "Stream/*", type = "pw-global" },
+        },
+        -- and device nodes that are not associated with any routes
+        Interest {
+          type = "node",
+          Constraint { "media.class", "matches", "Audio/*", type = "pw-global" },
+          Constraint { "device.routes", "equals", "0", type = "pw" },
+        },
+        Interest {
+          type = "node",
+          Constraint { "media.class", "matches", "Audio/*", type = "pw-global" },
+          Constraint { "device.routes", "is-absent", type = "pw" },
+        },
+      }
+
+   The above example will create an ObjectManager that matches all nodes with
+   a "media.class" global property that starts with the string "Stream/"
+   and additionally all those whose "media.class" starts with "Audio/" and
+   they have either a "device.routes" property that equals zero or they
+   don't have a "device.routes" property at all.
+
+   :param table interest_list: a list of :ref:`interests <lua_object_interest_api>`
+                               to objects
+   :returns: a new object manager
+   :rtype: ObjectManager (:c:struct:`WpObjectManager`)
+
+Methods
+~~~~~~~
+
+.. function:: ObjectManager.activate(self)
+
+   Activates the object manager.
+   Binds :c:func:`wp_core_install_object_manager`.
+
+   :param self: the object manager
+
+.. function:: ObjectManager.get_n_objects(self)
+
+    Binds :c:func:`wp_object_manager_get_n_objects`
+
+   :param self: the object manager
+   :returns: the number of objects managed by the object manager
+   :rtype: integer
+
+.. function:: ObjectManager.iterate(self, interest)
+
+   Binds :c:func:`wp_object_manager_new_filtered_iterator_full`
+
+   :param self: the object manager
+   :param interest: an interest to filter objects
+   :type interest: :ref:`Interest <lua_object_interest_api>` or nil or none
+   :returns: all the managed objects that match the interest
+   :rtype: Iterator; the iteration items are of type :ref:`GObject <lua_gobject>`
+
+.. function:: ObjectManager.lookup(self, interest)
+
+   Binds :c:func:`wp_object_manager_lookup`
+
+   :param self: the object manager
+   :param interest: the interest to use for the lookup
+   :type interest: :ref:`Interest <lua_object_interest_api>` or nil or none
+   :returns: the first managed object that matches the interest
+   :rtype: :ref:`GObject <lua_gobject>`