do not use class name publicly

[dbu]

the metadata drivers (i.e. xml driver) should read the "name" for a type from the metadata, instead of determining it from the class. this means that for every request, we will need to know the full list of mapped data - meaning we should start to cache compiled metadata for performance reason.

see AbstractRdfDriver::objectToName

[flack]

To some extent, this is already implemented in the array driver (see https://github.com/flack/createphp/blob/master/src/Midgard/CreatePHP/Metadata/RdfDriverArray.php#L207), although I'm not sure if this is good enough. We could add a name attribute to the type tag in XML easily enough, but I'm not yet sure how the lookup is supposed to work