TEIIDDES-1826 Corrects problem when single file is chosen in FlatFile Connection Profile

- The user is allowed to choose a single file in the Flat File Connection Profile, but we were not handling that case.  Now setting the 'ParentDirectory' property successfully for this case.
- The user is also allowed to enter a remote file URI in the Flat File connection profile.  More work is required in Designer for this scenario (need to utilize WebService RA instead of File RA, same as we do with XML).  
- Added checks for the URI case to let user know the local dir was not found