We are having an issue with the way the xliff format is implemented inside symfony2.
This was brought here before by @schmittjoh in #2252 but was closed down.

I'm proposing to do a BC break here and change the XLIFF to a format where translation tools are actually useful.
e.g. Because we use keys as our translation source the tools like www.getlocalization.com show those keys as a source to be translated which according to the xliff specification is the right thing to do.

<trans-unit id="<id>" resname="<resname>">
  <source>Original string</source>
  <target>Target language translation</target>
</trans-unit>

Where the < id > is somesort of unique id e.g hash of < resname >, The < resname > is set to translation key or "Original string" in case that translation is not based on the keys and the < source > tag contains the string in language the translations will be made from.