Plugins: Disable support for config dir

When removing and installing again the plugin all configuration files will be removed in `config/pluginname` dir.
This is bad as users may have set and added specific configuration files.

We don't have yet an upgrade command which could handle this nicely.

So we remove that code for now and we will implement an upgrade method in another PR.

Related to  #5064.
@dadoonet I don't think it complicates things that much.. it's just traversing the file tree...

and yes... sub-folders need to be supported as well. so if you see a folder with the same name/path in both places, recursively merge the two by adding the new files and skipping existing ones. I'd also argue that if in the es plugin config dir there's a file that doesn't exist in the new plugin dir structure, then rename it to "<original_file_name>.<original_extension>.old" (or something like that).