Add ability to customize cache folder

Add an advanced settings page, currently only housing the "Cache" category

Fix #541

src/singletons/Settings.hpp

@@ -153,6 +153,8 @@ public:
     IntSetting startUpNotification = {"/misc/startUpNotification", 0};
     QStringSetting currentVersion = {"/misc/currentVersion", ""};
 
+    QStringSetting cachePath = {"/cache/path", ""};
+
     void saveSnapshot();
     void restoreSnapshot();