Capitalise "SPM" and "FSL" software names in terms

This follows a discussion with @gllmflndn. `SPM` and `FSL` being acronyms, we would like to rename `nidm:Spm` and `nidm:Fsl` in `nidm:SPM` and `nidm:FSL`.

I have just checked and actually the capitalised versions are already in use in the NIDM-Results.owl vocabulary (cf. [nidm:SPM](https://github.com/ni-/ni-o/blob/master/nidm-results.owl#L1651) and [nidm:FSL](https://github.com/ni-/ni-o/blob/master/nidm-results.owl#L1404)) from the ni-o repository so that this pull request removes an inconsistency across the two repositories (ni-o / nidm).