Add a Site model?

[caendesilva]

Could be useful to have a data model to consolidate global site data, like internals such as the output path, and global metadata. Then in the meta views, we'd render $site->metadata and $page->metadata, thus splitting out the responsibilities.

[caendesilva]

If we split out the metadata, we'll likely need/want to diff out any overlapping metadata so page specific metadata gets priority over the globals