Review matrix config file

[RFSH]

When we migrated the matrix app to React, we didn't make any changes to its config properties. But now we should go back and see if we can make the properties to be aligned with what we designed for the plot app.

At the minimum, we should ensure we're not using camelCase; instead, we should _ to break words. Apart from this, given that heatmap is the closest to the matrix app, we should look at how we're using plot-config to create a heatmap. And see if we can modify the matrix-config properties to be more aligned with plot-config.