docs(structural-directives): <template> was replaced by <ng-template>

[wKoza]

Angular 4 uses now <ng-template> for structural directives. <template> is deprecated.

[wardbell]

Thank you. Great start. But there are still a lot more <template> and "template" references to fix, including in some of the docs you edited such as "structural-directives.jade". I know it's tough because not every use of the word "template" is wrong; only those that describe the element.

Let's get them all (or at least more of them) in this PR. Do you mind?

[wKoza]

@wardbell I've updated structural-directives.jade

[wardbell]

Thanks! I have a few more to correct but this gets most of them.