Url rules and other fixes

Adds initial, opinionated implementation of restful URL rules, so one

    array('class' => 'Restyii\Web\UrlRule'),

can replace the mess of URL rules we used to require.

PR also adds a default error action that presents the error in the correct response format - e.g. xml or json as appropriate.

Also includes a fix for the insert() method on `Restyii\Client\Resource\Model`