Update build.gradle to support Gradle 2.0

gradle/01-hello-muni/build.gradle

@@ -1 +1,6 @@
-apply plugin: 'cpp-exe'
+apply plugin: 'cpp'
+
+executables {
+    main {
+    }
+}

gradle/02-hello-muni-with-gradle-wrapper/build.gradle

@@ -1,3 +1,8 @@
-apply plugin: 'cpp-exe'
+apply plugin: 'cpp'
 
 task wrapper(type: Wrapper)
+
+executables {
+    main {
+    }
+}

gradle/03-hello-muni-with-debug/build.gradle

@@ -1,4 +1,4 @@
-apply plugin: 'cpp-exe'
+apply plugin: 'cpp'
 
 
 // Based on http://www.gradle.org/docs/current/userguide/nativeBinaries.html
@@ -12,3 +12,8 @@ binaries.all {
         linker.args '/DEBUG'
     }
 }
+
+executables {
+    main {
+    }
+}