Warn when someone applies the same plugin more than once

Originates in https://github.com/cssinjs/jss/issues/683

We should detect if plugin has been applied already and warn. To achieve this we could add a plugin name to each plugin, because we can't use hook refs

Start by reading the related issue #683 and tracing where plugins are applied in JSS. Determine how duplicate applications can be identified without hook references, then define the warning behavior and verify that repeated plugin application is detected without affecting a plugin applied once.

Written by the indexing model from the issue text.