Fixed several remaining file errors.  #1177

Presentations and galleries both had stupid errors where I'd mapped items incorrectly.  At least those were easy to fix.

Node abstract had a subtler problem.  For fields that take multiple values, I can give migrate an array.  In some cases like files, they require several arrays.  Creating a file has an array for each arg, like destination path, file exists behavior, etc.

Anyway, when we were getting to destination path and destination file name, migrate was treating the array like a single value.  Turns out destination_dir can't be used as an array arg.  If a node has 5 files, I can only give them one destination_dir string arg.  That seems like an odd design choice, but since we're homogenizing file paths it works in our case.

Destination file was similar, except that I couldn't specify it at all.  I had to remove it entirely and use the file itself as filename.  Wouldn't have figured this out on my own.  Thanks, google.  http://drupal.org/node/1673956

Was getting some errors about dirs not being creatable, but couldn't duplicate them after last few fixes.  Investigating further before trying to run this on staging.
Merge branch 'SCHOLAR-3-0' of github.com:openscholar/openscholar into SCHOLAR-3-0