Refactored how maps are written...

Opus now supports the following styles:

source/file => dest/            (results in dest/file)
source/file => dest/file2     (results in dest/file2)

The first example is true if the destination is a directory already or is
explicitely set with '/' (in which case it will be created)

source/dir => dest/dir2/       (results in dest/dir2/dir)
source/dir => dest/dir2        (results in dest/dir2)

Explicit trailing slash is required to copy a directory into another dir, even
if it already exists.