Use JSExportStatic for Angular annotations

[jokade]

Currently we generate a separate JS file with the annotations required by Angular (-sjsx.js'). With the advent of @JSExportStatic` in Scala.js 0.6.15 this should no longer be necessary.

[jokade]

OK, @JSExportStatic only works on @ScalaJSDefined classes, so we're currently stuck with the -sjsx file.