BAP-6792: Make tracking website entity extendable    - added info about work done to UPGRADE file
BAP-6792: Make tracking website entity extendable
   - added info about work done to UPGRADE file

Djamy/platform,ramunasd/platform,hugeval/platform,orocrm/platform,morontt/platform,northdakota/platform,Djamy/platform,ramunasd/platform,geoffroycochard/platform,hugeval/platform,Djamy/platform,trustify/oroplatform,orocrm/platform,geoffroycochard/platform,ramunasd/platform,morontt/platform,northdakota/platform,morontt/platform,trustify/oroplatform,2ndkauboy/platform,hugeval/platform,orocrm/platform,trustify/oroplatform,geoffroycochard/platform,2ndkauboy/platform,northdakota/platform,2ndkauboy/platform