Function checks if the trash item is a page or another object and calls the apropiate remove functions
The page object is special since cases like being a parent or being a homepage must be handled
This method extracts the SpaceKey from a String which should look like Spacekey:Pagename
This method is used as a helper method to parse the String given by the PagePicker which
is used by the parentPage form field as well as the moveAttachment.