this kinda works.. make docroot optional

This also sets variables to local in functions.
make logging optional
make the default php config optional in Nginx
break out fpm pools to own tab

This makes it possible to use the same fpm pool on multiple servers which
could be beneficial for certain use cases.
Merge pull request #2 from OpenMediaVault-Plugin-Developers/be-more-flexible

Try to make the plugin more flexible