Changed parent to org.jenkins-ci.plugins:plugin:1.424 to make build work in Java 7.

Full cause:

Plugin did not build in Java7:
	$ java -version
	java version "1.7.0_03"
	OpenJDK Runtime Environment (IcedTea7 2.1.1) (7~u3-2.1.1-1)
	OpenJDK 64-Bit Server VM (build 22.0-b10, mixed mode)

- Because it depended on an old version of "plugins". Which in turn
needed: com.sun.mirror.apt.AnnotationProcessorFactory, which was deprecated in Java 6 and removed in Java 7.

This caused "mvn clean package" under Java 7 to fail with:

[INFO] --- maven-hpi-plugin:1.54:apt-compile (default-apt-compile) @ locks-and-latches ---
okt 12, 2012 12:08:05 EM org.sonatype.guice.bean.reflect.Logs$JULSink warn
Varning: Error injecting: org.jvnet.hudson.maven.plugins.hpi.AptCompiler
java.lang.NoClassDefFoundError: com/sun/mirror/apt/AnnotationProcessorFactory
	at java.lang.Class.getDeclaredConstructors0(Native Method)
	at java.lang.Class.privateGetDeclaredConstructors(Class.java:2404)
	at java.lang.Class.getDeclaredConstructors(Class.java:1853)
	at com.google.inject.spi.InjectionPoint.forConstructorOf(InjectionPoint.java:245)
	at com.google.inject.internal.ConstructorBindingImpl.create(ConstructorBindingImpl.java:98)
	at com.google.inject.internal.InjectorImpl.createUninitializedBinding(InjectorImpl.java:629)
	at com.google.inject.internal.InjectorImpl.createJustInTimeBinding(InjectorImpl.java:831)
	at com.google.inject.internal.InjectorImpl.createJustInTimeBindingRecursive(InjectorImpl.java:758)
	at com.google.inject.internal.InjectorImpl.getJustInTimeBinding(InjectorImpl.java:255)
	at com.google.inject.internal.InjectorImpl.getBindingOrThrow(InjectorImpl.java:204)
	at com.google.inject.internal.InjectorImpl.getProviderOrThrow(InjectorImpl.java:954)
	at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:987)
	at com.google.inject.internal.InjectorImpl.getProvider(InjectorImpl.java:950)
	at com.google.inject.internal.InjectorImpl.getInstance(InjectorImpl.java:1000)
	at org.sonatype.guice.bean.reflect.AbstractDeferredClass.get(AbstractDeferredClass.java:45)
	at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:84)
	at com.google.inject.internal.InternalFactoryToInitializableAdapter.provision(InternalFactoryToInitializableAdapter.java:52)
	at com.google.inject.internal.ProviderInternalFactory$1.call(ProviderInternalFactory.java:70)
	at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:100)
	at org.sonatype.guice.plexus.lifecycles.PlexusLifecycleManager.onProvision(PlexusLifecycleManager.java:138)
	at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:108)
	at com.google.inject.internal.ProvisionListenerStackCallback.provision(ProvisionListenerStackCallback.java:55)
	at com.google.inject.internal.ProviderInternalFactory.circularGet(ProviderInternalFactory.java:68)
	at com.google.inject.internal.InternalFactoryToInitializableAdapter.get(InternalFactoryToInitializableAdapter.java:45)
	at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
	at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1018)
	at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
	at com.google.inject.Scopes$1$1.get(Scopes.java:59)
	at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
	at com.google.inject.internal.InjectorImpl$3$1.call(InjectorImpl.java:965)
	at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1011)
	at com.google.inject.internal.InjectorImpl$3.get(InjectorImpl.java:961)
	at org.sonatype.guice.bean.locators.LazyBeanEntry.getValue(LazyBeanEntry.java:83)
	at org.sonatype.guice.plexus.locators.LazyPlexusBean.getValue(LazyPlexusBean.java:49)
	at java.util.AbstractMap.get(AbstractMap.java:182)
	at org.codehaus.plexus.compiler.manager.DefaultCompilerManager.getCompiler(DefaultCompilerManager.java:54)
	at org.jvnet.hudson.maven.plugins.hpi.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:260)
	at org.jvnet.hudson.maven.plugins.hpi.CompilerMojo.execute(CompilerMojo.java:111)
	at org.jvnet.hudson.maven.plugins.hpi.AptMojo.execute(AptMojo.java:24)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:601)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)
Caused by: java.lang.ClassNotFoundException: com.sun.mirror.apt.AnnotationProcessorFactory
	at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:50)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:244)
	at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:230)
	... 60 more