Update docs to reflect Gradle plugin being available in the Plugin Portal

Closes gh-1567

spring-boot-docs/src/main/asciidoc/build-tool-plugins.adoc

@@ -172,32 +172,33 @@ dependency management provided by `spring-boot-dependencies`.
 
 [[build-tool-plugins-including-the-gradle-plugin]]
 === Including the plugin
+ifeval::["{spring-boot-repo}" == "release"]
+To use the Spring Boot Gradle Plugin configure it using the `plugins` block:
+[source,groovy,indent=0,subs="verbatim,attributes"]
+----
+	plugins {
+		id 'org.springframework.boot' version '{spring-boot-version}'
+	}
+----
+endif::[]
+ifeval::["{spring-boot-repo}" != "release"]
 To use the Spring Boot Gradle Plugin simply include a `buildscript` dependency and apply
 the `spring-boot` plugin:
 
 [source,groovy,indent=0,subs="verbatim,attributes"]
 ----
 	buildscript {
+		repositories {
+			maven { url 'http://repo.spring.io/snapshot' }
+			maven { url 'http://repo.spring.io/milestone' }
+		}
 		dependencies {
-			classpath("org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}")
+			classpath 'org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}''
 		}
 	}
 	apply plugin: 'org.springframework.boot'
 ----
-
-If you are using a milestone or snapshot release you will also need to add appropriate
-`repositories` reference:
-
-[source,groovy,indent=0,subs="verbatim,attributes"]
-----
-	buildscript {
-		repositories {
-			maven.url "http://repo.spring.io/snapshot"
-			maven.url "http://repo.spring.io/milestone"
-		}
-		// ...
-	}
-----
+endif::[]
 
 
 

spring-boot-docs/src/main/asciidoc/deployment.adoc

@@ -387,8 +387,6 @@ With Gradle, the equivalent configuration would be:
 
 [source,groovy,indent=0,subs="verbatim,quotes,attributes"]
 ----
-	apply plugin: 'org.springframework.boot'
-
 	springBoot {
 		executable = true
 	}

spring-boot-docs/src/main/asciidoc/getting-started.adoc

@@ -226,22 +226,28 @@ Here is a typical `build.gradle` file:
 
 [source,groovy,indent=0,subs="verbatim,attributes"]
 ----
+ifeval::["{spring-boot-repo}" == "release"]
+	plugins {
+		id 'org.springframework.boot' version '{spring-boot-version}'
+		id 'java'
+	}
+endif::[]
+ifeval::["{spring-boot-repo}" != "release"]
 	buildscript {
 		repositories {
 			jcenter()
-ifndef::release[]
-			maven { url "http://repo.spring.io/snapshot" }
-			maven { url "http://repo.spring.io/milestone" }
-endif::release[]
+			maven { url 'http://repo.spring.io/snapshot' }
+			maven { url 'http://repo.spring.io/milestone' }
 		}
 		dependencies {
-			classpath("org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}")
+			classpath 'org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}'
 		}
 	}
 
 	apply plugin: 'java'
 	apply plugin: 'org.springframework.boot'
 
+endif::[]
 	jar {
 		baseName = 'myproject'
 		version =  '0.0.1-SNAPSHOT'
@@ -249,10 +255,10 @@ endif::release[]
 
 	repositories {
 		jcenter()
-ifndef::release[]
+ifeval::["{spring-boot-repo}" != "release"]
 		maven { url "http://repo.spring.io/snapshot" }
 		maven { url "http://repo.spring.io/milestone" }
-endif::release[]
+endif::[]
 	}
 
 	dependencies {

spring-boot-docs/src/main/asciidoc/using-spring-boot.adoc

@@ -214,8 +214,6 @@ Maven, there is no "`super parent`" to import to share some configuration.
 
 [source,groovy,indent=0,subs="attributes"]
 ----
-	apply plugin: 'java'
-
 	repositories {
 ifeval::["{spring-boot-repo}" != "release"]
 		maven { url "http://repo.spring.io/snapshot" }
@@ -240,32 +238,33 @@ managed by Spring Boot:
 
 [source,groovy,indent=0,subs="attributes"]
 ----
+ifeval::["{spring-boot-repo}" == "release"]
+	plugins {
+		id 'org.springframework.boot' version '{spring-boot-version}'
+		id 'java'
+	}
+endif::[]
+ifeval::["{spring-boot-repo}" != "release"]
 	buildscript {
 		repositories {
-ifeval::["{spring-boot-repo}" != "release"]
-			maven { url "http://repo.spring.io/snapshot" }
-			maven { url "http://repo.spring.io/milestone" }
-endif::[]
-ifeval::["{spring-boot-repo}" == "release"]
 			jcenter()
-endif::[]
+			maven { url 'http://repo.spring.io/snapshot' }
+			maven { url 'http://repo.spring.io/milestone' }
 		}
-
 		dependencies {
-			classpath("org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}")
+			classpath 'org.springframework.boot:spring-boot-gradle-plugin:{spring-boot-version}'
 		}
 	}
 
 	apply plugin: 'java'
 	apply plugin: 'org.springframework.boot'
+endif::[]
 
 	repositories {
-ifeval::["{spring-boot-repo}" != "release"]
-		maven { url "http://repo.spring.io/snapshot" }
-		maven { url "http://repo.spring.io/milestone" }
-endif::[]
-ifeval::["{spring-boot-repo}" == "release"]
 		jcenter()
+ifeval::["{spring-boot-repo}" != "release"]
+		maven { url 'http://repo.spring.io/snapshot' }
+		maven { url 'http://repo.spring.io/milestone' }
 endif::[]
 	}