Implemented Give insight in Updater requests (frequency)

Give insight in how many request per minute / hour / day / etc. the ochSubscriptions Updater is serving to websites who have extensions installed.
Both for serving XML update files as well as download key validations

Currently this is not visible and this information is needed for making scaling decisions on you server setup.

Implemented logging for updater xml and (the new) changelog xml requests
todo: key validation requests

Added logging for Key Validate requests
Created config toggle for enabling / disabling these type of requests logging