Use Schema.org WebPage type for StaticContent

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no (except for consumers of the rdfa data)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7 
| License       | MIT

IMHO, the most adapted type is WebPage.