move argument handling from mainwindow.py to bin/secop-gui

allows calling the GUI client independently from command line arguments

Change-Id: If51b899c456ad610cf8a64f9b0f7c8a218cf5c5b
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22503
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

bin/secop-gui

@@ -58,7 +58,10 @@ def main(argv=None):
 
     app = QApplication(argv)
 
-    win = MainWindow()
+    hosts = [host for host in argv[1:] if not host.startswith('-')]
+    if not hosts:
+        hosts = ['localhost:10767']
+    win = MainWindow(hosts)
     win.show()
 
     return app.exec_()