Additional localization tests

[johlju]

Details of the problem, bug, or enhancement

There is localization tests added in PR #319. But there are a couple of additional tests that should be added. If possible we should also add the tests mentioned here PowerShell/DscResources#236 (comment)

Tests:

• All localized strings must have an ID.
• No string ID can be equal to any other string ID in the same file.
• The same string ID's should exists on the corresponding key in all localized language files.

Verbose logs showing the problem (if applicable)

n/a

Suggested solution to the issue

See details above.