REQ: Align texture location to the rest of the Quake ecosystem

[dsvensson]

For some reason ezQuake has taken its own route with regards to which paths texture loading checks compared to the rest of the ecosystem. Support should be added for additionally checking the same paths as for example FTE checks to make it more convenient to try out other clients without losing carefully crafted set of hud, model and map customizations.

Once aligned, nQuake ought to update its pk3's to make them compatible with both ezQuake and FTE.