[IMPR] Provide options by a separate handler class
[IMPR] Provide options by a separate handler class

- provide an option handler class
- derive BaseBot from OptionHandler class

There are som generator classes who could derive from OptionHandler:
- redirect.RedirectGenerator
- pagefromfile.PageFromFileReader
Will be done in a separate patch set.
- rewrite help message for redirect.py

Change-Id: Ib281147d38f3d6eaf34f1a1ad0c7c920513f0d79

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