determine value of "data" subpages

[aqw]

The data page will be entirely reworked. The general idea is that the demos in the "gists" are not necessary, and will likely be replaced with other demos (e.g. #16 and #27).

The question now is whether the /content/ on those pages is of value:

• Prolonged quasi-natural stimulation with an audio-movie
• T1-weighted MRI scans
• Susceptibility-weighted scans
• Time-of-flight inflow angiography
• T2-weighted MRI scans
• Diffusion tensor MRI scans
• Cortical surface reconstructions
• Movie structure annotations
• Speech annotation

[aqw]

The decision has been made: they all should be removed.

[aqw]

DONE.