Rework POM structure

Rework main build POM to be an aggregator pom that does not inherit
from any parent. Introduce new spring-boot-dependencies module to
act as a parent for both spring-boot-starter-parent and
spring-boot-parent.

spring-boot-samples/pom.xml

@@ -6,6 +6,7 @@
 		<groupId>org.springframework.boot</groupId>
 		<artifactId>spring-boot-parent</artifactId>
 		<version>0.5.0.BUILD-SNAPSHOT</version>
+		<relativePath>../spring-boot-parent</relativePath>
 	</parent>
 	<artifactId>spring-boot-samples</artifactId>
 	<packaging>pom</packaging>
@@ -30,6 +31,13 @@
 	<build>
 		<pluginManagement>
 			<plugins>
+				<plugin>
+					<groupId>org.apache.maven.plugins</groupId>
+					<artifactId>maven-deploy-plugin</artifactId>
+					<configuration>
+						<skip>true</skip>
+					</configuration>
+				</plugin>
 				<plugin>
 					<groupId>${project.groupId}</groupId>
 					<artifactId>spring-boot-maven-plugin</artifactId>