PEP257 on pywikibot folder part I

files: bot, date and editor.
Checked by hand and added some suggestions based on this change:
I910fdd7ce36752fa44b9a6654d7b8509e5020dee

Change-Id: I59a2b271bee8c0a9a37db28ef0fa66f69ad30412
Merge "PEP257 on pywikibot folder part I"