Add Support for VTAU LookupTable

[joselfrias]

In the context of a project with Gates Ventures, we encountered a specific tool, VisualTAU, that requires the application of a specific LUT in the image display to be FDA-approved.
The goal is to identify the areas of activity in a PET Image of the brain given by a radioactive drug, TAUVID, which is extremely useful to evaluate biormarkers for the presence of Alzheimer's disease.
This PR adds this LUT to FreeBrowse.

Summary

• Adds ColorMap/LUT for VTAU (converted from a file that is applied using FreeView)
• Adds respective mappings to allow VTAU to be chosen in the dropdown of the left menu in the imaging UI

[pwighton]

Thanks for the PR!

I've simplified the VTAU lookup table, and changed the alpha value of the lowest intensities to 0 so that the 3d rendering does something resonable.

I've submitted a PR to BMDSoftware:imp/add_vtau_lut with this change: BMDSoftware/pull/1

Can you confirm that this looks good on your end, and if so, accept the PR? After that PR is resolved, I'll accept this one.

[pwighton]

More information on niivue colormaps: https://github.com/niivue/niivue/blob/main/docs/development-notes/colormaps.md

[joselfrias]

Hi Paul,

We tested your changes and it looks good, we can now see the 3D rendering and the Color Map for VTAU was heavily simplified! We merged those changes in this contribuition.

Thank you!