Schema.org tags

[gregzaal]

SEO optimization - include some additional metadata on some pages according to schema.org spec. Check sharetextures.com for reference.

[fulopkovacs]

I'll check this one out next week.

If anyone's interested, this is how a schema looks like for a model on sharetextures.com:
https://search.google.com/test/rich-results/result/r%2Farticles?id=FCZHDOeaOoJjYNPK0F6cLw

[fulopkovacs]

Had an idea about solving another issue, so I worked on that this week: #64

I might get back to this issue, after that PR is done.