Keymap: Remove pie menu from tab-key

Based on discussion with @eyecandy & @venomgfx,
we agreed that Tab drag/click, is too easy to accidentally press
while moving the cursor.
It's also not typical to activate the operator on release which
introduces a small lag switching edit-mode.

This is a shame since in some ways its a nice way to re-use the key,
overall it just feels a little too unpredictable for such an important
action.

This commit makes the following changes.

- Tab: toggles edit-mode.
- Ctrl-Tab: opens pie menu.
- Ctrl-AccentGrave: toggles manipulator.

Note, while AccentGrave isn't always available
this shortcut is not essential.

source/blender/editors/object/object_ops.c

@@ -293,11 +293,11 @@ void ED_keymap_object(wmKeyConfig *keyconf)
 	keymap = WM_keymap_find(keyconf, "Object Non-modal", 0, 0);
 
 	/* modes */
-	kmi = WM_keymap_add_item(keymap, "OBJECT_OT_mode_set", TABKEY, KM_CLICK, 0, 0);
+	kmi = WM_keymap_add_item(keymap, "OBJECT_OT_mode_set", TABKEY, KM_PRESS, 0, 0);
 	RNA_enum_set(kmi->ptr, "mode", OB_MODE_EDIT);
 	RNA_boolean_set(kmi->ptr, "toggle", true);
 
-	kmi = WM_keymap_add_menu_pie(keymap, "VIEW3D_MT_object_mode_pie", TABKEY, KM_CLICK_DRAG, 0, 0);
+	kmi = WM_keymap_add_menu_pie(keymap, "VIEW3D_MT_object_mode_pie", TABKEY, KM_PRESS, KM_CTRL, 0);
 
 #ifdef USE_WM_KEYMAP_27X
 	WM_keymap_add_item(keymap, "OBJECT_OT_origin_set", CKEY, KM_PRESS, KM_ALT | KM_SHIFT | KM_CTRL, 0);

source/blender/editors/space_view3d/view3d_ops.c

@@ -531,7 +531,7 @@ void view3d_keymap(wmKeyConfig *keyconf)
 #ifdef USE_WM_KEYMAP_27X
 	kmi = WM_keymap_add_item(keymap, "WM_OT_context_toggle", SPACEKEY, KM_PRESS, KM_CTRL, 0); /* new in 2.5 */
 #else
-	kmi = WM_keymap_add_item(keymap, "WM_OT_context_toggle", TABKEY, KM_PRESS, KM_CTRL, 0);
+	kmi = WM_keymap_add_item(keymap, "WM_OT_context_toggle", ACCENTGRAVEKEY, KM_PRESS, KM_CTRL, 0);
 #endif
 	RNA_string_set(kmi->ptr, "data_path", "space_data.show_manipulator");