GPencil: Change default Onion Keyframe mode to ALL

Now by default the selection mode is All keyframes types.

Also removed the icon for All option and renamed from `All Types`to `All`.

UI review by @pablovazquez

release/scripts/startup/bl_app_templates_system/2D_Animation/__init__.py

@@ -55,6 +55,13 @@ def load_handler(dummy):
                     space.shading.type = 'MATERIAL'
                     space.shading.use_scene_world = True
 
+    # Grease pencil object
+    scene = bpy.data.scenes[0]
+    if scene:
+        for ob in scene.objects:
+            if ob.type == 'GPENCIL':
+                gpd = ob.data
+                gpd.onion_keyframe_type = 'ALL'
 
 def register():
     bpy.app.handlers.load_factory_startup_post.append(load_handler)

source/blender/blenkernel/intern/gpencil.c

@@ -532,6 +532,7 @@ bGPdata *BKE_gpencil_data_addnew(Main *bmain, const char name[])
   gpd->grid.lines = GP_DEFAULT_GRID_LINES;            /* Number of lines */
 
   /* Onion-skinning settings (data-block level) */
+  gpd->onion_keytype = -1; /* All by default. */
   gpd->onion_flag |= (GP_ONION_GHOST_PREVCOL | GP_ONION_GHOST_NEXTCOL);
   gpd->onion_flag |= GP_ONION_FADE;
   gpd->onion_mode = GP_ONION_MODE_RELATIVE;

source/blender/makesrna/intern/rna_gpencil.c

@@ -106,7 +106,7 @@ static const EnumPropertyItem rna_enum_keyframe_type_items[] = {
 };
 
 static const EnumPropertyItem rna_enum_onion_keyframe_type_items[] = {
-    {-1, "ALL", ICON_ACTION, "All Types", "Include all Keyframe types"},
+    {-1, "ALL", 0, "All", "Include all Keyframe types"},
     {BEZT_KEYTYPE_KEYFRAME,
      "KEYFRAME",
      ICON_KEYTYPE_KEYFRAME_VEC,