Fix #17012 - iscolor() renamed color_input() and documented

Presentation, rationale, discussion, other options

#17012
color_input name: could also be colorinput (as colorbar and colordef), colorcheck, colorCheck, ...

Documentation

https://gitlab.com/scilab/scilab/uploads/ee65e08a0fb5b88370bcd2598a85634b/color_input.pdf

cleaning

iscolor will be replaced and removed in Scilab after merging this MR.