StringConstants: Add class

The StringConstants class contains much used strings. This
has the significant advantage that they do not need to be
translated several times in slightly different versions.
StringConverter: Add the class
StringConverter: Add test
TestHelper: Seperate tests visually
StringConverterTest: Test an unknown bool val
Merge pull request #45 from sils1297/wip/misc

Miscellaneous changes pribarily in the misc package