citra_qt/applets/swkbd: QtKeyboard and misc fixes

* Addressed comments and removed the applet interface

* swkbd: address @lioncash's comments

* core: more fixes

** Moved registered_swkbd to System

** Removed an usused virtual

** Removed functionality of DrawScreenKeyboard

** Removed src/core/settings.h change

* swkbd: address @lioncash's 2nd review

* swkbd: update logging macro

* QtKeyboard: Make dialog modal and hide help

src/citra_qt/main.cpp

@@ -16,6 +16,7 @@
 #include <QtGui>
 #include <QtWidgets>
 #include "citra_qt/aboutdialog.h"
+#include "citra_qt/applets/swkbd.h"
 #include "citra_qt/bootmanager.h"
 #include "citra_qt/camera/qt_multimedia_camera.h"
 #include "citra_qt/camera/still_image_camera.h"
@@ -1470,6 +1471,7 @@ int main(int argc, char* argv[]) {
 
     // Register frontend applets
     Frontend::RegisterDefaultApplets();
+    Frontend::RegisterSoftwareKeyboard(std::make_shared<QtKeyboard>(main_window));
 
     main_window.show();
     return app.exec();