ZCML "provides" support

When defining a generic setup profile, we have a ZCML like:

```xml
<configure>

    <genericsetup:registerProfile
        name="default"
        ...
        provides="Products.GenericSetup.interfaces.EXTENSION"
        />

</configure>
```

The attached changes add support for detecting "provides" attributes in ZCML
in general, which will result in getting ``Products.GenericSetu`` detected properly.


Detect ZCML "provides", as used for generic setup profile registration.