Fix #6238 Return blank arrays 

I committed this simple change to return the empty array rather than false for empty settings result for ElggPlugin::getAllSettings and getAllUsersSettings. Put this into 1.8 branch.
Handle case if get_user_notification_settings() returns false
Merge pull request #6250 from edfactor/patch-1

Makes sure plugin settings functions return arrays
Fixes #6012: Gets correct client IP behind proxy (1.8)
Checks X-Real-Ip header as well when determining client IP
Code style fixes for recent PR