www/grafana5: create port for grafana 5.x

Grafana is an open source, feature rich metrics dashboard and graph editor for
Graphite, ElasticSearch, OpenTSDB, Prometheus and InfluxDB.

WWW: https://github.com/grafana/grafana

This port is for the 5.x version of Grafana, based on the port for 4.x. Also
made changes to pet port line while here.

Submitted by: David O'Rourke
Differential Revision: https://reviews.freebsd.org/D14602