Added to NIDM-R spec, mostly sections 2.1.1.1-2.1.1.3
Merge pull request #60 from dbkeator/master

Added to NIDM-R spec, mostly sections 2.1.1.1-2.1.1.3
Update "undefined" examples
Comment "extended structure"

To be updated later on
Overview of SPM-specific entities and attributes
Overview of FSL-specific attributes
Automatically-generated SPM- and FSL-specific

(in section 4)