Add support of autoscale policy to modify command

[idrabenia]

_As SDK user I want to have possibilities to modify autoscale policy against with other server settings by single API call_

Proposed syntax is

serverService
    .modify(
        ...
        .machine(new Machine()
            .cpu(4)
            .ram(16)
            .autoscalePolicy("Policy1")
        )
        ...
    );