[IMPR] Always import pywikibot in shell.py by default
[IMPR] Always import pywikibot in shell.py by default

- Don't import pywikibot if -noimport option is given
- If additional options are given with -noimport
  print a message that they are ignored
- If pywikibot is imported and arguments are given print a message
  that they are unknown if they couldn't be handled by handle_args

Bug: T194456
Change-Id: I19262a9e24ce5f0e8515353b1750bae0de83de12

PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core,wikimedia/pywikibot-core