Perform initial refactoring work

Things that were once singletons are no longer singletons, but are
instead stored in the "Application" singleton

Some singletons still remain, and some renaming/renamespacing is left

src/singletons/pathmanager.hpp

@@ -7,13 +7,10 @@ namespace singletons {
 
 class PathManager
 {
-    PathManager();
+    PathManager(int argc, char **argv);
+    friend class Application;
 
 public:
-    static PathManager &getInstance();
-
-    bool init(int argc, char **argv);
-
     // %APPDATA%/chatterino or ExecutablePath for portable mode
     QString settingsFolderPath;