[reSIProcate] more complete support for RFC 3455 headers and parameters?

[John Gregg]

A quick grep in resip/stack for the string "3455" shows that there is 
native resiprocate support for P-Called-Party-ID and P-Associated-URI, 
but no others (like P-Charging-Vector, P-Charging-Function-Addresses, 
etc.) or their associated parameters ("ecf", "ccf"). Is there a reason 
for this? If I add more of these RFC 3455 headers and parameters, should 
I bundle up the diff files and post them here for possible inclusion in 
future releases?

-John Gregg