NcRichContenteditable pasting HTML alike content strips off text

[susnux]

Maybe related to #3264 but even worse:

Pasting HTML alike content strips content instead of replacing it with the HTML entities,
For example pasting

```java
Test<Object> myMethod() {
}
```

Will result in:

```java
Test myMethod() {
}
```

[Antreesy]

Paste was solved with #3915, but rendering is broken:

• at second NcRichContenteditable (not a big deal, unlikely there will be two components linked to the single data source)
• inside multiline code block at NcRichText with markdown

Styleguide	Talk app

Full list of escaped characters is here: https://html.spec.whatwg.org/multipage/named-characters.html