ENH: added fetch_spm_auditory_data(...), fetch_fsl_feeds_data(...), and ...

Added some fetchers that I've had around for a while now. Precisely, these are fetchers for:
- SPM auditory single subject (lagacy dataset, bad quality, but good for demos/examples)
- SPM Multimodal fmri faces vs scrambled (I worked with @alex senior on this dataset recently)
- FSL (FEEDS single subject)