Gideon : Added a new test SoftSyntacticConstraintDecodingTest.java
that tests if soft syntactic constraint decoding matches, by checking if
the alternate derivations that are expected from soft matching of labels
are indeed generated. Currently this test still fails, as the new functionality is not
yet implemented. We are now thus well prepared to implement the new functionality.

As part of the effort to implement this new test, we also refactored the old
test code of ArtificialGrammarAndCorpusCreater and added new supporting classes
TestConfigFileCreater.java and ArtificialGrammarAndCorpusCreater.java that take care
of producing the required test files automatically.