Shorthands - closes #29

[ju1ius]

I had to change the implementation of CSSRuleSet.
The rules list is now a numerically indexed array instead of an associative array.
This allows us to have things like this:

p {
  border-style: solid !important;
  foobar: baz;
  border-style: none;
}

And then do this:

foreach($oRuleSet->getRules('border-style') as $position => $rule) {
  printf("%d => %s", $position, $rule);
}
/*
0 =>  border-style: solid !important;
2 => border-style: none;
*/
echo $oRuleSet->getAppliedRule('border-style');
/*
border-style: solid !important;
*/

This allows expand/createShorthands to get around some edge cases.

[sabberworm]

I don’t know what I was thinking when I implemented CSSRuleSet as an associative array; I should have thought of vendor-specific values and the !important flag. I would still, however, like to stick with the existing API as closely as possible, e.g. passing ('font-') instead of ('font', true) to removeRule and getRule (and revert the name change from removeRule to remove).

[sabberworm]

This would also return textism: none when asked for ('text', true) where the old code would not when asked for ('text-').