Updated pl.dir.file_op to return true on success and false on failure when falling back to DOS commands.

The fallback to DOS commands (when alien is not available) now returns false,err on failure and true on success as stated in the documents.
Tests for copying have been added and move has been updated.
Merge pull request #102 from chrisjaquet/Updated-return-values-for-pl.dir

Updated pl.dir.file_op to return true on success and false on failure...