[IMPR] Remove '.py' before matching the string
[IMPR] Remove '.py' before matching the string

- Improve string matching by removing '.py' ending.
  See T217195 for further information.
- Also ignore __init__.py scripts
- use set to hold the script names to hold the script path
  (used later to let the user the choice to start it)

Bug: T217195
Change-Id: I3952cb77191890cface75bdb5a51e7c2613f63ac

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