code improvements

- check for a valid speedy deletion template on live wiki. The
  result is hold in the class container so we need to check only
  once.
- use Site instead of Site.lang as key for twn dictionaries
  this should also solve that bug pointed out at
  https://sourceforge.net/p/pywikipediabot/bugs/1577/
  i18n library uses the right code even the key would be changed
  from code to lang on twn dict in future or there might be a
  fallback from code to lang on i18n library.
- test whether we are logged in as sysop because we have no
  exception here like in compat

Change-Id: I39dd03bc04846f129ee20c7959a57e4685e87d94
Merge "code improvements"