[Fluxus] colour commits

[gabor papp]

i committed some colour changes. now all expressions containing colours 
  should expect values in four formats:

(vector .9411 .2352 .145) ; rgb
(vector .3784 .4411 .9039 .5) ; rgba
.5 ; greyscale
(vector 1 .3) ; greyscale + alpha

i also modified the hsv code and made it a bit more logical i hope.

usage of (opacity) is still not perfect. it overwrites colour alpha 
elements of the current state if the opacity value is other than the 
default 1.0. i assumed if the value is not 1.0, the user is using the 
(opacity) function.

please test the colour system. all comments are welcome.

best,
gabor