MovieClip: Make name of Active Clip consistent in UI

Using the currently active movie clip had different names in the interface:
In scene context it was "Active Movie Clip", in Camera Background Images it was "Camera Clip", in Constraints it was "ActiveClip".
I made all those instances use "Active Clip", which is descriptive enough and also the shortest of the three.

Reviewed By: billreynish

Differential Revision: https://developer.blender.org/D5400

release/scripts/startup/bl_ui/properties_data_camera.py

@@ -289,7 +289,7 @@ class DATA_PT_camera_background_image(CameraButtonsPanel, Panel):
             elif bg.source == 'MOVIE_CLIP' and bg.clip:
                 row.prop(bg.clip, "name", text="", emboss=False)
             elif bg.source and bg.use_camera_clip:
-                row.label(text="Camera Clip")
+                row.label(text="Active Clip")
             else:
                 row.label(text="Not Set")
 
@@ -329,7 +329,7 @@ class DATA_PT_camera_background_image(CameraButtonsPanel, Panel):
                             sub.template_image_stereo_3d(bg.image.stereo_3d_format)
 
                 elif bg.source == 'MOVIE_CLIP':
-                    box.prop(bg, "use_camera_clip")
+                    box.prop(bg, "use_camera_clip", text="Active Clip")
 
                     column = box.column()
                     column.active = not bg.use_camera_clip

release/scripts/startup/bl_ui/properties_scene.py

@@ -63,7 +63,7 @@ class SCENE_PT_scene(SceneButtonsPanel, Panel):
 
         layout.prop(scene, "camera")
         layout.prop(scene, "background_set")
-        layout.prop(scene, "active_clip")
+        layout.prop(scene, "active_clip", text="Active Clip")
 
 
 class SCENE_PT_unit(SceneButtonsPanel, Panel):