WIP: Update SPM model

As agreed on PR #20:
* Replace `prov:atLocation` by `prov:location`
* Replace `nidm:hasCoordinateSpace` by `nidm:coordinateSpace`

Added:
* New attribute `statisticType` in `contrast_id` to specify whether we are dealing with an F-test or T-test (or other…)
* New attribute `nidm:statisticalTest` in `inference` to specify if the type of test (in particular one-tailed or two-tailed for T-tests)

Fix:
* Remove `contrastName` in `betaMap_2`
* Change `prov:label` in `contrast_id` to be coherent with `prov:type`