Standardize Build

The build now uses spring build conventions to simplify the build

Fixes gh-4284

docs/manual/spring-security-docs-manual.gradle

@@ -0,0 +1,11 @@
+apply plugin: 'io.spring.convention.docs'
+
+asciidoctor {
+	def ghTag = snapshotBuild ? 'master' : project.version
+	def ghUrl = "https://github.com/spring-projects/spring-security/tree/$ghTag"
+	attributes 'spring-security-version' : project.version,
+		'spring-version' : project(':spring-security-core').dependencyManagement.managedVersions['org.springframework:spring-core'],
+		revnumber : project.version,
+		'gh-url': ghUrl,
+		'gh-samples-url': "$ghUrl/samples"
+}