add ImageGenerator and UnCategorizedTemplateGenerator
add ImageGenerator and UnCategorizedTemplateGenerator

ported from compat branch

APISite.uncategorizedtemplates() was available since
https://www.mediawiki.org/wiki/Special:Code/pywikipedia/9843
but had no corresponding pagegenerators

renamed UnCategorizedTemplatesGenerator
   into UnCategorizedTemplateGenerator
for consistency reasons, as:
* UnCategorizedCategoryGenerator
* UnCategorizedImageGenerator
* UnCategorizedPageGenerator

bug: 55007
Change-Id: I961310f6b3f13f1ac3880857e0f454576a0cbce6

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