[FIXED JENKINS-22568] Subversion polling does not work with parameters.

Currently subversion polling does not work with parameters. This code changes polls using the _DEFAULT_ option. If there is a choice parameter, it will choose the _FIRST_ option. This will also expand anything that is `$VAL` or `${VAL}`.
@christ66 could probably do that... but IIRC the correct utility is actually in a plugin because there are multiple ways to expand tokens or something... anywho I'll leave it up to @christ66 how he wants to respond