Better HTML5 conformance

[averms]

Four minor changes to the templates to improve HTML5 conformance. Here is the commit log

State canonical URL using <link> not <meta>.

The Google SEO docs describe using the link element to specify the canonical
page in a redirect. They don't mention anything about <meta>.

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Fix formatting of content attr in <meta http-equiv=refresh>

According to the HTML specification[1], there needs to be a space after the
semicolon and the URL must be unquoted.

[1]: https://html.spec.whatwg.org/multipage/semantics.html#attr-meta-http-equiv-refresh

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Don't generate obsolete charset attrs in <script>.

According to the HTML specification[1], the charset attribute is obsolete in
script elements.

[1]: https://html.spec.whatwg.org/multipage/obsolete.html#HTMLScriptElement-partial

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Don't generate redundant <meta http-equiv=content-type>.

Quoting from the HTML specification[1]:

> A document must not contain both a meta element with an http-equiv attribute
> in the Encoding declaration state and a meta element with the charset
> attribute present.

So we remove the <meta> with the http-equiv attribute from our template.

[1]: https://html.spec.whatwg.org/multipage/semantics.html#attr-meta-http-equiv-content-type

[ehuss]

Thanks!