Finally, a quality plugin

This update finally adds support for statically-defined item qualities. Not sure what purpose this serves since this doesn't get you the dynamic qualities at runtime from entities, but since TF2ItemsInfo and TF2IDB both support this, I guess it must be done.

But, now that it's done, I think the plugin now has a feature set that fully matches (and rivals) those of the schema-info-retrieving plugins that were available prior.

There's a few more API tweaks that I think are worth adding, but The Big One-Point-Oh is Soon™.

Added

• Native TF2Econ_GetItemQuality, which returns the statically-defined quality value for the given item definition index.

Changed

• Minor changes to offset discovery notes, which should improve finding those offsets again.