fix(compiler): always wrap views into an own `<template>` element

This is needed to allow view instantiation also in browsers that
don’t support the `<template>` element and because of this would
return elements from the content of `<template>` elements when
using `element.querySelectorAll`.

Also stores the `elementBinder.nestedProtoView` correctly
when a template directive was used on a `<template>` element.
fix(compiler): allow identifiers with `-` in the template bindings as keys.
feat(viewport): add initial integration test for template directives