Feature/git no tags

[mathiasburger]

The git plugin supports a noTags option which is especially useful in combination with shallow. In fact without noTags shallow copies can get quite big.

In this PR I added the noTags option to the job dsl. The tests were extended and I tested the plugin on my local jenkins instance by creating a freestyle job with a "Process Job DSLs" task like this:

    scm {
      git {
        remote {
          name('origin')
          url('git://github.com/quidryan/aws-sdk-test.git')
        }
        extensions {
          cloneOptions {
            shallow()
            noTags()
          }
        }
      }
    }
    triggers {
        scm('H/15 * * * *')
    }
    steps {
        maven('-e clean test')
    }
}