FIX Filter searched files by site
FIX Filter searched files by site

As well as restricting pages by SiteID, restrict searched files by site folder
path to prevent data leakage

Added config option to disable this behaviour

Zauberfisch/silverstripe-multisites,xini/silverstripe-multisites,stephenmcm/silverstripe-multisites,Zauberfisch/silverstripe-multisites,silverstripe-australia/silverstripe-multisites,silverstripe-australia/silverstripe-multisites,xini/silverstripe-multisites,stephenmcm/silverstripe-multisites