Adds new "ambiguous" statement, changes "supported" to "equivalent"

[tonypconway]

This PR changes two things.

• The 'supported' value has been changed to "equivalent" to indicate that the webview has the same level of support as the corresponding browser. Sometimes the corresponding browser doesn't support the feature completely or at all, and the webview support is the same so "equivalent" is a more appropriate name.
• Some keys have unexpected results, like the webview supporting the feature where the corresponding browser does not. for the time being, I'm marking these features as "ambiguous" so they can be reviewed. Only 9 web-features IDs trigger this state, so it's not a major concern, but it does need to be investigated.