ENYO-1740, ENYO-1890: Dropbox, implement MOVE & COPY

- implement `FsDropbox.copyOrMove()`,
  `FsDropbox.copy()`,
  `FsDropbox.move()`

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>