Redefeind interfaces; Added better modelled data strauctures

Router interface has been redefined which fits better with what we are
looking for.

Routing table now offers a comprehensive set of information about its
entries which will make up for rich queries in the future

Query interface has been defined to enable current basic and more
advanced queries in the future.

router/options.go

@@ -2,7 +2,6 @@ package router
 
 import (
 	"context"
-	"time"
 
 	"github.com/micro/go-micro/registry"
 )
@@ -15,17 +14,33 @@ type Options struct {
 	Context context.Context
 }
 
-// RouteOption allows to soecify routing table options
-type RouteOption struct {
-	// TTL defines route entry lifetime
-	TTL time.Duration
-	// COntext allows to specify other arbitrary options
-	Context context.Context
-}
-
-// Registry is local registry
+// Registry allows to set local service registry
 func Registry(r registry.Registry) Option {
 	return func(o *Options) {
 		o.Registry = r
 	}
 }
+
+// RouteOptions allows to specify routing table options
+type RouteOptions struct {
+	// NetID is network ID
+	NetID string
+	// Metric is route metric
+	Metric int
+	// COntext allows to specify other arbitrary options
+	Context context.Context
+}
+
+// NetID allows to set micro network ID
+func NetID(id string) RouteOption {
+	return func(o *RouteOptions) {
+		o.NetID = id
+	}
+}
+
+// Metric allows to set route cost metric
+func Metric(m int) RouteOption {
+	return func(o *RouteOptions) {
+		o.Metric = m
+	}
+}