Added named parameters referenceing to defaultParams in CUrlRule

This change to CUrlRule which adds almost no additional overhead allows
referencing named parameters in defaultParams options.
This works for both URL creation and parsing.

The rationale is to simplify writing rules which are often similar
but distinguish themselves by a file extension or a common word
which is contained in the pattern and also in the defaultParams option.

Consider this example which whithout the change would require 3 rule
entries:

'products/software-manual.<ext:(pdf|chm|doc)>' => array(
'resources/download',
'urlSuffix'=>'',
'defaultParams'=>array('file'=>'doc1234.<ext>')