Use listbox for device-specific advanced menu items

This patch allows items to have more than one action surrounded
by the <actions> tags like other GUI elements. The patch also
adds new twrp command line options that let you reload the theme
and switch to a specific page from the command line:

adb shell twrp reloadtheme
adb shell twrp changepage=advanced

Change-Id: I838ea380a508be07b9fa617034d1954e116febd6
diff --git a/gui/listbox.cpp b/gui/listbox.cpp
index 9d36bae..9fbe092 100644
--- a/gui/listbox.cpp
+++ b/gui/listbox.cpp
@@ -102,8 +102,10 @@
 		item.selected = (child->value() == currentValue);
 		item.action = NULL;
 		xml_node<>* action = child->first_node("action");
+		if (!action)
+			action = child->first_node("actions");
 		if (action) {
-			item.action = new GUIAction(action);
+			item.action = new GUIAction(child);
 			allowSelection = true;
 		}
 		xml_node<>* variable_name = child->first_node("data");