Remove "Voxel to World Mapping" in voxel-to-world-mapping definition
Perform SPM export tests
fix: missing found_range
add: summary level database descriptor
add: summary level project descriptor
add: version level descriptor
add: distribution level component descriptor
add: distribution level aggregate descriptor
rm: generic descriptor
add: experiment project level
add: experiment study question level
add: experiment mr study level
add: experiment acquisition level
voxelToWorldMapping definition updated as suggested by @nicholst
Merge pull request #148 from cmaumet/voxelToWorldMapping

Definition of "voxelToWorldMapping"
Remove SPM export testing (moved to incf-nidash/nidm-results_spm)
Merge pull request #122 from cmaumet/extentTests

Merge: Automatic testing of NIDM export in SPM
fix: /path/to replaced by relative path
fix: MaskMap was missing
update mask_map_ids to fit with what is exported in SPM (useful for test only)