Moving files by dragging now possible

moveFile function added - takes oldName and newName and moves to that.
Also performs tab renaming as per rename function
updateFileManagerList function has new move event to add at new location
and remove from old
dropFile function updated to kickstart all of this with new moveFile
function call
Move event added

If we're due to move a file and it's writable, rename it to new location
Call move event once done to update file list
Show message if we failed or clear server message if all is OK