PoFileDumper - PO headers
bug #9223 [Translator] PoFileDumper - PO headers (Padam87)

This PR was submitted for the master branch but it was merged into the 2.2 branch instead (closes #9223).

Discussion
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[Translator] PoFileDumper - PO headers

| Q             | A
| -------------  | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #6765 - partially
| License       | MIT
| Doc PR        |

Po files should not be dumped without a header. It causes a lot of problems, including charset issues.

See #6765 / 1 for more info

Commits
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e93bc50 [Translator] PoFileDumper - PO headers