Mark the inactive libraries properly inside the packages report

Due to the PHP compatibility reasons some libraries can be attached to the project in an inactive state - without the composer.json file 'autoload' section.

Such libraries do not have any effect to the project. However, due to missing autoload section they are marked as an UNKNOWN library type warning inside the packages report at the moment - which could be confusing to the users.

Let's change this warning to INACTIVE notice instead. And let's add the proper explanation to Ludwig 'read more' documentation what does it mean exactly.