issue369: make it simpler to enter filenames.

Add .sfd to files without an extension of either sfd or sfdir
if that happens then place a warning in the log to that effect.
moved to the GFileNameTail() function, added the docs to that function
and included a you might have been looking for basename note to help
future users.
Merge pull request #1572 from monkeyiq/2014/aug/369

issue369: make it simpler to enter filenames.