[CSS21] [CSSOM] property values and component values

At the last F2F
   http://lists.w3.org/Archives/Public/www-style/2010Apr/0274.html
it was requested to have different terms to distinguish the
property's value from the one or more value components that
make it up. In the current specs, both are called "value".
The CSSOM especially needs to be able to distinguish the two.

I had an action item to make a diff against CSS2.1, which I am
attaching here. Since we chose the terms "property value" and
"component value" to allow both to be shortened to "value",
there were very few changes actually needed.

This is CSS2.1 Issue 166:
   http://wiki.csswg.org/spec/css2.1#issue-166

~fantasai