Added functionality to deploy using delegate role capability of AWS

[ajayrammohan]

I have added the functionality to use the delegate role concept of AWS. This is useful if a deployment is necessary in a delegate account.

The changes in the gradle file of the application will be as follows

Before

beanstalk {
profile = 'default'
s3Endpoint = "s3-eu-west-1.amazonaws.com"
beanstalkEndpoint = "elasticbeanstalk.eu-west-1.amazonaws.com"

deployments {
    staging {
        war = aaa.war
        application = 'appName'
        environment = 'appName-env'
    }

    prelive {
        war = aaa.war
        application = 'appName'
        environment = 'appName-prelive'
    }
}

}

After

beanstalk {
profile = 'default'
s3Endpoint = "s3-eu-west-1.amazonaws.com"
beanstalkEndpoint = "elasticbeanstalk.eu-west-1.amazonaws.com"

deployments {
    staging {
        war = aaa.war
        application = 'appName'
        environment = 'appName-env'
    }

    prelive {
        account = 'accountName'
        arnRole = 'arnRole'
        war = aaa.war
        application = 'appName'
        environment = 'appName-prelive'
    }
}

}

[ajayrammohan]

beanstalk {
profile = 'default'
s3Endpoint = "s3-eu-west-1.amazonaws.com"
beanstalkEndpoint = "elasticbeanstalk.eu-west-1.amazonaws.com"

deployments {
staging {
war = aaa.war
application = 'appName'
environment = 'appName-env'
}

prelive {
    account = 'accountName'
    arnRole = 'arnRole'
    s3Endpoint = "s3-endpoint"
    beanstalkEndpoint = "elasticbeanstalk.endpoint"
    war = aaa.war
    application = 'appName'
    environment = 'appName-prelive'
}

}
}

[komu]

Oh, and I just dived into my comments and completely forgot to say: thanks for the pull request! :)

[ajayrammohan]

Made changes according to review findings.

Happy to contribute :)