added private share api
add a "helper" and a "hooks" class. Move constants needed by multiple classes
to a "constants" class
remove prepFileTarget() seems that it is no longer in use
add code directly to "getItemsSharedWith()"
add code directly to getItemsShared()
once more getItemsSharedWith
fix comparisons
add code directly to getItemSharedWith(), move code to format the result to a
seperate method
ported fix #7393