Improve Explorer URL management

Each distribution holds a "key" metadata used for the URL, additional aliases would be useful to allow using more than one URL (and avoid hardcoding redirections inside apache conf)

Solen says:

I assume that it's because of the Nuxeo DM-7.10 instead of Nuxeo Platform-7.10, URLs like http://explorer.nuxeo.com/nuxeo/site/distribution/Nuxeo%20Platform-7.10/viewExtensionPoint/org.nuxeo.ecm.core.io.MarshallerRegistry--marshallers are redirected to a cap-8.1 distribution (http://explorer.nuxeo.com/nuxeo/site/distribution/cap-8.1/viewExtensionPoint/org.nuxeo.ecm.core.io.MarshallerRegistry--marshallers).