Logs

I added first logs for PDI core. I don't how many and detailed logs we want in debug and info level.

To make logger work in plugins I had to add it as parameter, because plugins compilation is separated from PDI.

Also I had to add condition to m_logger initialization (Logger m_logger {spdlog::get("logger") ? spdlog::get("logger") : spdlog::stdout_color_st("logger")};), because unit tests don't call PDI_Init where logger is created.

@jbigot Could you review the MR and tell what to change?