Fix problems with examples discovered by CSE436 class at Cal Poly.

Examples/Echo/PackageManager/Sources/echo.grpc.swift

@@ -0,0 +1 @@
+../../Generated/echo.grpc.swift

Examples/Google/NaturalLanguage/Sources/main.swift

@@ -16,6 +16,7 @@
 import Foundation
 import gRPC
 import OAuth2
+import Dispatch
 
 let scopes = ["https://www.googleapis.com/auth/cloud-language"]