Feature/schemify get properties parent filters

[kylereicks]

Call the filter schemify_get_properties_{$schema} for each of a schema's ancestors when Schemify\Schemas\{Schema}\getProperties is called.

Use case: I wanted to add the post content to the articleBody property for the Article schema and any children like BlogPosting. Currently, if I add a schemify_get_properties_Article filter, it is not called from BlogPosting\getProperties.