Deprecate punct plugin

The functionality of the [punct](https://github.com/logstash-plugins/logstash-filter-punct) plugin is a subset of what the [fingerprint](https://github.com/logstash-plugins/logstash-filter-punct) filter does with `method => "PUNCTUATION"`.

Unless we think it's very important to keep plugins nice and small I suggest we deprecate the punct plugin. It's rather buggy and I'd prefer putting effort into getting rid of it rather than doing copy/paste of code and tests from the fingerprint plugin.