Fix Python 3 tests.
Enhance tests.
Merge branch 'master' into learning3

Conflicts:
	Code2Xml.Core.Tests/Generators/SyntaxTreeGeneratorTest.cs
	Code2Xml.Languages/ANTLRv3.Tests/CSharpCstGeneratorTest.cs
	Code2Xml.Languages/ANTLRv3.Tests/JavaCstGeneratorUsingAntlr3Test.cs
	Code2Xml.Languages/ANTLRv3.Tests/JavaScriptCstGeneratorTest.cs
	Code2Xml.Languages/ANTLRv3.Tests/LuaCstGeneratorUsingAntlr3Test.cs
	Code2Xml.Languages/ANTLRv3.Tests/PhpCstGeneratorTest.cs
	Code2Xml.Languages/ExternalPrograms.Tests/Python2CstGeneratorTest.cs