#430 Output directory created if does not exist

[Kim Hanisak]

Currently, if you set an output gapfilled surrogate
file to a directory that does not exist an error
message occurs stating that the file can not open.

It might be good to have the program be able to create
the directory by default if it does not exist, thus
allowing the output file to be created in the new
directory without requiring the user to set up the
directory first.