Old-Style C++ documentation and missing BOB_TRY

In the C++ code of this module, the documentation does not rely on the bob::extension documentation classes. Furthermore, bob.io.matlab.read_varnames will crash on exceptions, as they are not caught: https://gitlab.idiap.ch/bob/bob.io.matlab/blob/master/bob/io/matlab/main.cpp#L29

• Update documentation to use the bob::extension documentation classes
• Use BOB_TRY and BOB_CATCH_FUNCTION to catch exceptions in the binding code