Add plot of MD/FA as function of microstructural parameter

This proposes to rearrange the plots into a 3x3 grid of plots with:

• the first row showing mean signal as a function of b-value, diffusion time, and user-selected microstructural parameter
• the second row showing MD/FA as a function of the same variables as the first row
• the third row showing the ODF (and containing the dropdown menus to select the microstructural parameter) The design is attached below.

The plots as a function of microstructural parameters will be new. The rest will just be a rearranging of the existing ones into a more structured grid.