veyron/tools: Merge the impl and main packages

This change gets rid of the impl packages and moves the impl.go files to
the main package for each tool under veyron/tools/.

Change-Id: Ieae4bc1dd02296f58f8cb6327b903d025cf833f5
diff --git a/tools/build/main.go b/tools/build/main.go
index 6b96081..a99a159 100644
--- a/tools/build/main.go
+++ b/tools/build/main.go
@@ -13,12 +13,9 @@
 	"veyron.io/veyron/veyron2/rt"
 
 	_ "veyron.io/veyron/veyron/profiles"
-	"veyron.io/veyron/veyron/tools/build/impl"
 )
 
 func main() {
-	r := rt.Init()
-	defer r.Cleanup()
-
-	impl.Root().Main()
+	defer rt.Init().Cleanup()
+	root().Main()
 }