tests: rm duplicate code in language classes

tests: rm duplicate code in language classes

The language classes have been using the same setUp() tearDown() to
craft a new language object. I have abstracted that code in
LanguageClassesTestCase and made all the language test classes to extend
it. The language is interpolated directly from the class name and an
object for it can be retrieved with the getLang() method.

Change-Id: Ib931336ce219edabe2c72b7e9f04c976a500723e