Allow duplicate resource url

Added a parameter in gpt.xml:

```
 	<parameter key="AllowDuplicateResourceURL" value="true"/>
```
When set to true it allows to register web resources with same URL. This is useful to register the same resources with different profiles, that can be tailored to include filters. If the parameter is false or is not set than the default behaviour is follwed, i.e. URL must be unique.