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/widgets/emotepopup.hpp

@@ -12,7 +12,7 @@ namespace widgets {
 class EmotePopup : public BaseWindow
 {
 public:
-    explicit EmotePopup(singletons::ThemeManager &);
+    EmotePopup();
 
     void loadChannel(ChannelPtr channel);
     void loadEmojis();