ni-/ni-dm — pull request #49 by cmaumet (2014-05-06 09:58:15+00:00)
Title: Merge: Delete underlayFile attribute

Following issue #46, and as agreed on [NIDASH-DDWG call on 28th of April](https://docs.google.com/document/d/1p1eV5PvNvEz001rIckDGq9I5ez-8oafZrKokJZH8ijM/edit?usp=sharing) this pull request deletes the `nidm:underlayFile` attribute.