Add multi-file delete, move and copy to Movie Player

[prl]

Currently delete, move and copy only work on the recording/media file with focus. For move and copy, a multi-file operation requires the user to specify the destination for each operation.

Add the ability to mark items in the file list, and apply delete, move and copy operations to all marked items.

If no items are marked, then the operation is on the item in focus.

This is similar to the similar operations in the DP series File Player.

This feature should not require a separate screen as is the case in the File Commander (I will also add an Enhancement Request for the File Commander to not use two screens to support single and multi-file operations).