GUI: Support styles in xml to reduce xml file size

Also allow sliders to have their own text label instead of
requiring a whole separate text object for the label in the xml.

Change-Id: I6e314efb4bb454d496555ff7e003d743063a1308
diff --git a/gui/pages.hpp b/gui/pages.hpp
index 31ccadb..8eec9a9 100644
--- a/gui/pages.hpp
+++ b/gui/pages.hpp
@@ -102,6 +102,8 @@
 	int SetKeyBoardFocus(int inFocus);
 	int NotifyVarChange(std::string varName, std::string value);
 
+	std::vector<xml_node<>*> styles;
+
 protected:
 	int LoadPages(xml_node<>* pages);
 	int LoadVariables(xml_node<>* vars);
@@ -153,6 +155,8 @@
 
 	static HardwareKeyboard *GetHardwareKeyboard();
 
+	static xml_node<>* FindStyle(std::string name);
+
 protected:
 	static PageSet* FindPackage(std::string name);