Make the Oncoprint colors configurable (and persistant)

[alisman]

The cells of the oncoprint feature colors/shapes. The colors correspond to the categories in the legend. Users want to be able to customize these colors (at granularity of the legend). Not the shape/glyphs, but just the colors. One potential user interface would be to add drop down to the legend items that would allow a user to set colors.

• Find where in the codebase the current colors are determined
• Add an ability to override those colors based on settings persisted in the user session (global to user, not study specific)
• Build a simple UI to let user edit those settings

One additional feature:

• Some option to select background of glyphs to be white instead of gray (when all cases are profiled no need to distinguish between gray vs white)