[css3-multicol] Column Breaks

http://www.w3.org/TR/2007/WD-css3-multicol-20070606/#column5

I'm not quite convinced that we need separate properties for
column breaking. If the use case is forcing a column break, then
I think adding keywords to page-break-before and page-break-after
should be sufficient. If the use case is offering a different
level of breaking restrictions for columns than for pages, then
we also should have column-break-inside, column-windows, and
column-orphans.

I do think that if we have separate properties, the default value
should be defined such that it references the page-break-*
properties. That way, unless I really want separate sets of rules
for the two types of breaks, I only have to set the breaking
behavior once. This is particularly important when using the
'avoid' values.

What happens when there's a column break that's also a page break?
Do we use the page-break properties to control breaking behavior
or the column-break properties, or some combination thereof?

~fantasai