[Feature Request] Colorize HEX values

[PROPHESSOR]

In radare2 there's color highlighting for hex values (green for 0x00, red for 0xFF, blue for 0x7F, yellow for ASCII, etc).

It's convenient when you work with non-ascii data to "feel" the values.

In addition, it would be nice to have some heatmap-like gradient colorization of the values. For example, from blue for 0x00, through red for 0x7F, to white for 0xFF.

[solemnwarning]

Still an early WIP, but a preview of how the UI for this is coming along:

The intent here is that you will be able to define different value colourisation profiles which define solid colours to use for bytes, or start/end colours to apply a gradient over a range and switch between them from the view menu.

[solemnwarning]

[solemnwarning]

Finished and merged into master.