Multi Language frontend bug fix

[DavidBelicza]

Magento 2 does not translate frontend error messages. These changes fix this bug.

[LucScu]

@antboiko @piotrekkaminski
What does it means "The Travis CI build failed" ?

[DavidBelicza]

@LucScu It means the Magento develop branch does not pass the CI tests: https://travis-ci.org/magento/magento2

[LucScu]

@doveid Why it fails if the pull request is only string modifications?

[DavidBelicza]

@LucScu I recommend you to read about git branching how works the basics of git.

[LucScu]

@doveid I know how git works, i don't understand why string modifications do fail the CI? Or the fail is caused by other thing?

[LucScu]

@doveid Why CI check is now passed with same changes?

[antboiko]

@doveid thank you for your contribution, we have ticket MAGETWO-55058 to process this PR.

Best,
Anton.

[adragus-inviqa]

/cc #4038

Lots of duplicates here.

[vkorotun]

Internal ticket: MAGETWO-56553

[vkorotun]

Hey @doveid can you check with the latest mainline if these phrases aren't being fixed/translated already, since we've merge another similar PR and made some fixes internally.
Thx.