Expose loading animation icons through AllIcons

iconset/iconAccessorSpec.properties

@@ -168,6 +168,13 @@ Window.Maximize                     = window/maximize.svg
 Window.Minimize                     = window/minimize.svg
 Window.Restore                      = window/restore.svg
 
+Progress.Pause                      = progress/pause.svg
+Progress.Pause|disabled             = progress/pauseDisabled.svg
+Progress.Play                       = progress/resume.svg
+Progress.Play|disabled              = progress/resumeDisabled.svg
+Progress.Step                       = progress/stepWorking.svg
+Progress.Step|passive               = progress/stepPassive.svg
+
 Misc.ColorWheel                     = menu/colorChooser.svg
 Misc.Palette                        = misc/palette.svg
 Misc.Palette|disabled               = misc/paletteDisabled.svg