Implementing generic parser plugins and documentation

This constitutes a large change in how we will parse different data
formats going forward (for the plugins that support it)

This is working off @henrypfhu's changes.

cmd/telegraf/telegraf.go

@@ -11,6 +11,7 @@ import (
 
 	"github.com/influxdata/telegraf/agent"
 	"github.com/influxdata/telegraf/internal/config"
+
 	_ "github.com/influxdata/telegraf/plugins/inputs/all"
 	_ "github.com/influxdata/telegraf/plugins/outputs/all"
 )