[IMPR] Improvements for interwikidata.py
[IMPR] Improvements for interwikidata.py

- Add doc for already implemented option -summary.
- Align explanation to the same column like for -help documentation
- Add additional TODO hint (a separate phab task will be done).
- fallback is enabled by default for i18n.twtranslate
- Simplify arg parsing.

Change-Id: I5a1629c4708a4c08898dc5f50977512859e6157e

wikimedia/pywikibot-core,jayvdb/pywikibot-core,happy5214/pywikibot-core,hasteur/g13bot_tools_new,magul/pywikibot-core,Darkdadaah/pywikibot-core,PersianWikipedia/pywikibot-core,hasteur/g13bot_tools_new,npdoty/pywikibot,jayvdb/pywikibot-core,magul/pywikibot-core,wikimedia/pywikibot-core,Darkdadaah/pywikibot-core,happy5214/pywikibot-core,hasteur/g13bot_tools_new,npdoty/pywikibot