Latest gradle syntax updates.

samples/cas/cas.gradle

@@ -1,5 +1,5 @@
-apply id: 'war'
-apply id: 'jetty'
+apply plugin: 'war'
+apply plugin: 'jetty'
 
 dependencies {
     runtime project(':spring-security-core'),

samples/contacts/contacts.gradle

@@ -1,7 +1,7 @@
 // Contacts sample build file
 
-apply id: 'war'
-apply id: 'jetty'
+apply plugin: 'war'
+apply plugin: 'jetty'
 
 dependencies {
     providedCompile 'javax.servlet:servlet-api:2.5@jar'

samples/openid/openid.gradle

@@ -1,7 +1,7 @@
 // OpenID sample build file
 
-apply id: 'war'
-apply id: 'jetty'
+apply plugin: 'war'
+apply plugin: 'jetty'
 
 dependencies {
     providedCompile 'javax.servlet:servlet-api:2.5@jar'

samples/tutorial/tutorial.gradle

@@ -1,7 +1,7 @@
 // Tutorial sample build file
 
-apply id: 'war'
-apply id: 'jetty'
+apply plugin: 'war'
+apply plugin: 'jetty'
 
 dependencies {
     providedCompile 'javax.servlet:servlet-api:2.5@jar'