Add jenkins::plugin defined resource type

This commit adds jenkins::plugin which can be used
to install jenkins plugins. I used it to install
gearman just today:

  jenkins::plugin { 'gearman-plugin':
    version => '0.0.3',
  }

Note: this code is borrowed from:

  https://github.com/jenkinsci/puppet-jenkins/blob/master/manifests/plugin.pp

which is apache licensed.

Change-Id: Ifd3f6452839db990357f14665f14aa839ec2d0c5

modules/jenkins/manifests/plugin.pp

@@ -0,0 +1,55 @@
+#
+# Defined resource type to install jenkins plugins.
+#
+# Borrowed from: https://github.com/jenkinsci/puppet-jenkins
+#
+
+define jenkins::plugin(
+  $version=0,
+) {
+  $plugin            = "${name}.hpi"
+  $plugin_dir        = '/var/lib/jenkins/plugins'
+  $plugin_parent_dir = '/var/lib/jenkins'
+
+  if ($version != 0) {
+    $base_url = "http://updates.jenkins-ci.org/download/plugins/${name}/${version}"
+  }
+  else {
+    $base_url   = 'http://updates.jenkins-ci.org/latest'
+  }
+
+  if (!defined(File[$plugin_dir])) {
+    file {
+      [
+        $plugin_parent_dir,
+        $plugin_dir,
+      ]:
+        ensure  => directory,
+        owner   => 'jenkins',
+        group   => 'jenkins',
+        require => [Group['jenkins'], User['jenkins']],
+    }
+  }
+
+  if (!defined(Group['jenkins'])) {
+    group { 'jenkins' :
+      ensure => present,
+    }
+  }
+
+  if (!defined(User['jenkins'])) {
+    user { 'jenkins' :
+      ensure => present,
+    }
+  }
+
+  exec { "download-${name}" :
+    command  => "wget --no-check-certificate ${base_url}/${plugin}",
+    cwd      => $plugin_dir,
+    require  => File[$plugin_dir],
+    path     => ['/usr/bin', '/usr/sbin',],
+    user     => 'jenkins',
+    unless   => "test -d ${plugin_dir}/${name}",
+    notify   => Service['jenkins'],
+  }
+}