Check PO files

[matsduf]

There are several things that should be looked for in the PO files before they are accepted. The following tests should be executed:

• Verify that the PO file is correctly formated.
• Verify that every parameter in the msgid is also used in the `msgstr´.
• Verfy that no undefined parameter is used in the `msgstr.
• Verify that there are no "fuzzy" entries.
• Verify that there are no untranslated entries, i.e. for every msgid there must be a non-empty msgstr.

There are at lease two use cases:

• The translator should be able to verify that the PO file fully updated before it is submitted as a pull request. For this there should be a simple command line script, preferably executable with a make command from the share directory where other PO file operations are done.
• A pull request should be verified to make sure that the PO file is fully updated before it is merged. That is probably best done as unit tests, which are executed by Travis when pull requests are created.

[mattias-p]

I believe all of these have been fixed except for number 5. @matsduf Can you verify and update accordingly?

[matsduf]

I will run some tests to see what has been implemented and what remains. I will create a new issue of what remains, if necessary.