Updated Shader Menu (& Colormaps)

Updated shader menu

No longer uses lots of sliders. uses a preset systems with clickable previews that are modifyable.

Needs to test

• everything is working in the shaders menu (creating, modifying, quality of presets, ...)
• The menu allows to modify any previously modified shader
• The rendering options in the Tools menu is still working, and contains the "picked" and "multiselected" shaders.

Also needs to test the ColorMap menu

• able to create a colormap for a particular dataset (only when logged in).
• able to share it with others
• able to download a colormap as text
• able to upload a colormap from file (NOT working in standalone)

And look for any unforseen effects on other parts of the code. should be tested on WebGL and Standalone

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• Colormaps : change UI comments positionning and Z-index for lisibility
• Colormaps : make the download option directly download a file
• Colormaps : remove download button for "none"
• Colormaps : update the colormap grid with the new colors
• Colormaps : change the JSON for color parameters
• GUI : make final result preview more visible, maybe put it on the left of the whole interface