Updated article: Declaring character encodings in HTML

This update brings the article in line with recent developments in HTML5, and de-emphasizes information about legacy formats.

An attempt was also made to organize the material so that readers can find information more quickly, and also de-clutter the essential information by moving edge topics, such as UTF-16 and charset links, down the page. This led to the article being almost completely rewritten.

A new boilerplate and styling has also been applied to the article.

German, Spanish, Russian, Swedish and Ukrainian translators are asked to update their translation of this article within the next month, otherwise the translations will be removed per the translation policy, since the changes are substantive.