New SPM export.
Merge remote-tracking branch 'guillaume/master' into updateNIDMfileNaming
Rename spm_nidm.* in nidm.*
Merge pull request #1 from cmaumet/updateNIDMfileNaming

Update NIDM files naming
Rename object attributes.
Add dct prefix.
Add Map entities.
Add cluster_label_map_id and maximum_intensity_projection_id.
Add mask_map_id.
Add dct attributes.
Add further dct attributes.
Fix for wasDerivedFrom statements.
StatisticImageProperties moved to SearchSpace
Adding SearchSpace mask image.
Fix dct attributes.
Merge branch 'master' into guillaumemaster