Remove old rejected features

[dstorey]

scriptExecutionEvents have long since been removed from the spec. Imports doesn't have wide support and has been replaced in this test by ES Modules.

This PR removed those rejected features to not clutter the test up with old features.

[NielsLeenheer]

I'd like to keep the feature detects in the engine.js file. Even though these features would be invisible to any visitor of HTML5test and wouldn't get any points, I can still track whether or not browsers support it.

[dstorey]

makes sense, but should they be removed from the actual results and compare page?

[SC1040-TS2]

I would think, @dstorey, as it would make sense to include them in the results and Compare pages to allow the less programming-inclined page visitors to view and assess them, given the implications of supporting Rejected specifications such as the aforementioned Script execution events.

Though, maybe their point value should be universally marked as X (Web SQL Database still isn't), or otherwise have a note much like the ones for the Directories and System API and Web SQL Database features added to signify their deprecation, and the lack of benefit in supporting them.

[dstorey]

I would argue that things like SEE have been long forgotten about considering they're in no spec people can look up and have not been implemented by most browsers.

[niutech]

I've merged this PR into my HTML5Test fork.