vimc: Add color descriptions to test image

[Kaaira Gupta]

Hi!

Currently there is no method to know if the test image generated by vimc
is correct (except for comparing it with a known 'correct' image). So, I
wanted to investigate about a possibility to add text to each color bar
of the generated pattern. I think currently vivid supports this
functionality as an optional control, so can we move it to a common 
platform so that both VIVID and VIMC can supoort it?

Thanks,
Kaaira