Start flattening Qtlib into qt

- Remove app.py from qtlib (unused)
- Remove .gitignore from qtlib (unecessary)
- Move contents of preferences.py in qtlib to qt, clean up references
- Simplify language dropdown code

run.py

@@ -16,7 +16,7 @@ from PyQt5.QtWidgets import QApplication
 from hscommon.trans import install_gettext_trans_under_qt
 from qtlib.error_report_dialog import install_excepthook
 from qtlib.util import setup_qt_logging
-from qtlib.preferences import create_qsettings
+from qt.preferences import create_qsettings
 from qt import dg_rc  # noqa: F401
 from qt.platform import BASE_PATH
 from core import __version__, __appname__
@@ -74,7 +74,7 @@ def main():
     app.setWindowIcon(QIcon(QPixmap(f":/{DupeGuru.LOGO_NAME}")))
     global dgapp
     dgapp = DupeGuru()
-    install_excepthook("https://github.com/hsoft/dupeguru/issues")
+    install_excepthook("https://github.com/arsenetar/dupeguru/issues")
     result = app.exec()
     # I was getting weird crashes when quitting under Windows, and manually deleting main app
     # references with gc.collect() in between seems to fix the problem.