Bug 55055: category.py add -to: option
Bug 55055: category.py add -to: option

Feature request: -to: option is now possible not only for "move"
but also for "add".

Some clean-up and naming alignement done as well.

Change-Id: I85d022f3721601583ff3b3535bc81e6df2a0571d

happy5214/pywikibot-core,h4ck3rm1k3/pywikibot-core,magul/pywikibot-core,trishnaguha/pywikibot-core,hasteur/g13bot_tools_new,Darkdadaah/pywikibot-core,valhallasw/pywikibot-core,emijrp/pywikibot-core,hasteur/g13bot_tools_new,magul/pywikibot-core,jayvdb/pywikibot-core,wikimedia/pywikibot-core,happy5214/pywikibot-core,icyflame/batman,darthbhyrava/pywikibot-local,hasteur/g13bot_tools_new,TridevGuha/pywikibot-core,h4ck3rm1k3/pywikibot-core,smalyshev/pywikibot-core,jayvdb/pywikibot-core,Darkdadaah/pywikibot-core,VcamX/pywikibot-core,npdoty/pywikibot,xZise/pywikibot-core,npdoty/pywikibot,wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core