enlarge the size of settings dialog
enlarge the size of settings dialog

In some languages, the size of settings dialog is too small to show
the settings.

Close #421.

lucius-feng/seafile-client,lucius-feng/seafile-client,haiwen/seafile-client,daodaoliang/seafile-client,wgaalves/seafile-client,wgaalves/seafile-client,wgaalves/seafile-client,haiwen/seafile-client,lucius-feng/seafile-client,cloudcopy/client,cloudcopy/client,haiwen/seafile-client,haiwen/seafile-client,daodaoliang/seafile-client,losingle/seafile-client,wgaalves/seafile-client,daodaoliang/seafile-client,lucius-feng/seafile-client,cloudcopy/client,cloudcopy/client,daodaoliang/seafile-client,losingle/seafile-client,losingle/seafile-client,losingle/seafile-client