i18n XLIFF 2.0 serializer should add source files

[martinroob]

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Current behavior
Starting with angular 4.1 there is the new XLIFF 2.0 serializer available (#14185).
And there is also the new feature for writing a source reference into the xlf and xmb files (#14705).
But in XLIFF 2.0 this reference to source is not written.

Expected behavior
Add functionality for #14705 to the new XLIFF 2.0 serializer.

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Please tell us about your environment:

• Angular version: 4.1.X

• Browser: [all | Chrome XX | Firefox XX | IE XX | Safari XX | Mobile Chrome XX | Android X.X Web Browser | iOS XX Safari | iOS XX UIWebView | iOS XX WKWebView ]

• Language: [all | TypeScript X.X | ES6/7 | ES5]

• Node (for AoT issues): node --version =

[martinroob]

Just as a hint for implemting it.
In principle this information should be stored in the resourceData part.
But this is very complex and difficult to use.

So it migth be easier to just put source file and line information to a note element.

Something like this:

    <unit id="1409816038285774052">
      <notes>
        <note category="description">description</note>
        <note category="meaning">meaning</note>
	<note category="location">/home/user/sampleapp/src/app/app.component.ts:10</note>
      </notes>
      <segment>
        <source>My text</source>
      </segment>
    </unit>

[martinroob]

Oops, I did not want to close it.

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