Fix for #528.  Updates how custom types are dumped in Query.
Fix for #528.  Updates how custom types are dumped in Query.

* If a query involves a custom type, the property value must be dumped via the custom type API.
* Query's with custom types in a Query::Path are handled as a special case.

datamapper/dm-core,joevandyk/dm-core,tpitale/dm-core,ar-dm/ardm-core,engineyard/dm-core,tillsc/dm-core,alloy/dm-core