Changelog update
Remove Medialfy plugin

Mediafly has been out of service for a year or more.
Default stats reporting to opt-in

Don't load module unless reporting is enabled at startup. Should save a
few bytes and CPU cycles in LMS.
Only load prefs syncing code when needed
Merge branch 'public/7.8' into public/feature/no-slimservice

Change-Id: I74ecff5dadc02ad7b9944c898acb0ec0dbe152c7