Change portable folder to Qt's "Application dir path"

Enable portable mode if there's a "portable" file or folder in the
Application dir path

Fix #334

src/singletons/pathmanager.hpp

@@ -14,8 +14,13 @@ public:
 
     bool init(int argc, char **argv);
 
+    // %APPDATA%/chatterino or ExecutablePath for portable mode
     QString settingsFolderPath;
+
+    // %APPDATA%/chatterino/Custom or ExecutablePath/Custom for portable mode
     QString customFolderPath;
+
+    // %APPDATA%/chatterino/Cache or ExecutablePath/Cache for portable mode
     QString cacheFolderPath;
 
     // Logs