Fix InsertParagraph bugs and add newline after block on codeview.

`insertParagraph`
* Remove empty anchors on enter key press.
* range.deleteContents: remove empty parents.
* Fix bug: new line does not have previous line formatting on firefox, `range.normalize`
* blockquote is also bodycontainer.

`codeview`
* codeview: add newline on block element.