Context sensitive insertHtml

[Garry Yao]

We've seen various paste problems caused by our current implementation of CKEDITOR.editor::insertHtml, now rely on browsers' native API, which is buggy and inconsistent.
While we do have other options here: The idea is to implement an DTD aware, context sensitive insertion based on CKEDITOR.htmlParser' and 'CKEDITOR.editor::insertElement', this should be able to extinguish all weird bugs around.

Related tickets are:

#5367

Implement editor.insertText and use it in the special chars dialog

#5536

Problems with pasting (executing insertHtml) and formatted text

#5170

Problems with pasting (executing insertHtml) and formatted text

#5033

Invalid behavior when inserting nested divs with insertHtml()

#4898

Paste: After pasting a table from word it is not possible to navigate outside the table

#4746

insertHtml left trim text

#3105

insertHtml and insertElement should agree on the result

#2781

FckEditor InsertHtml inserts extra <p> tags

#2749

InsertHtml() is inconsistent between IE 7 and Firefox 2

#2526

InsertHTML Problem

#503

Unordered list paste: doesn't work correctly in IE

[Garry Yao]

Minor adjustments.

[Garry Yao]

By checking the ​insertHtml API in latest HTML5 draft, it also doesn't require a context sensitive insertion:

4. Invoke the HTML fragment parsing algorithm with an arbitrary orphan 'body' element owned by the same Document as the context element and with the value argument as input.

[Garry Yao]

We're over burdened now so this feature will be deferred to next milestone.

[Garry Yao]

Ported a simplified version of Firefox's ​nsHTMLEditor::InsertHTMLWithContext while it supposed to be browser neutral paste implementation.