Fix default template parameters

[kwabenantim]

• Supports Fix unable to find declarations #3

Changes

• Changed CppTypeInfo.decl : declaration_t to CppTypeInfo.decls : List[declaration_t] to hold multiple declarations for template instantiations.
• Try quering for class declarations without default template args if the full form is not found e.g. try Foo<2> if Foo<2,2> is not found and Foo is templated like <A, B=A>.
• Added a test for the above with a mesh example.
• Changed CppModuleWrapperWriter.exposed_class_full_names: List[str] to CppModuleWrapperWriter.class_decls : List[pygccxml.declarations.class_t] to use the found declaration above for subsequent queries instead of the instantiated class name.
• For clarity, separated the class discovery step (when module_info.use_all_classes == True) from the step associating each class (whether discovered or manually specified) with their correct declaration(s).