EXT-4957 : add const correctness for LLFolderViewEventListener::isItemRemovable
This checkin affects several files but is a lot less scary than it looks. It's mostly to add const correctness, and to rename isInTrash to isItemInTrash so that its naming is consistent with isItemRemovable/isItemMovable.
The only functionality change is to disable the trash button when an item is already in the trash.