Add support fort plugin-category and better code for type-category (Hostname/Plugin-PCategory-PInstance/Type-TCategory-TInstannce)
Tested with collectd 5 on curl_json (configure Instance to "PCategory-PInstance" to simulate plugin-category)
It's also working with genericJmx (TypeCategory in collectd4, I must test this on collectd 5)
Also fix a small bug with dynamic_dashboard when updating a filter