DataInterpreter: Add visual hex color interpretation

[schrmh]

It would be nice if the DataInterpreter could display a visual color of the selected block values (needs #213 first).
E.g. on three selected blocks RGB and on four RGBA (maybe ARGB alternatively).
Alternatively (or additionally) a color name could be displayed to give a hint but visual is better I would say.

[schrmh]

How a similar thing looks in Imhex (with mouse pointer over the RGBA8 color):

In this case it just takes the next four values from the cursor position. Guess this is just simpler anyways than having to select four blocks.

[EUA]

Since data interpretation section became enormous with addition of date-time section that enabled at last trunk,
might be it's good to have a options dialog to customize which values gonna how than allow RGBA8 and RGB565 color selections.