colormap need user level func to set colorindices

[doutriaux1]

Bill Hayes reported:

v = vcs.init()
cm = v.createcolormap('cm', 'default')
cm.color = 0, 99,99,99     # does NOT set the color  (but does not error)

However the following works to set and get values:

cm.index[0] = [99,99,99]   # this works
cm.index[0]    # returns the RGB list

THe user here is using internal/private functions
The correct call is

v.setcolormap(cm.name)
v.setcolorcell(0,99,99,99)

However, since 2.2 graphic methods are allowed to have their own colormap so we should have actual function on the colormap object to set the colors (rather that the private ones only)