Features and bugfix release

This is a minor update release with some new functionality and a few bugfixes. Most noably:

• Added

  WithHostName("my custom hostname")

  on the ContainerBuilder.

• Added SHELL and COPY on filebuilder to build a Dockerfile. Therefore it is now possible
  to write e.g. this in a FileBuilder

    Fd.DefineImage("mariotoffia/issue111").ReuseIfAlreadyExists()
              .From("microsoft/windowsservercore:1607")
              .Shell("powershell", "-Command", "$ErrorActionPreference = 'Stop';")
              .Run("powershell [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; exit 0")
              .Run(
                "Set-ExecutionPolicy Bypass -Scope Process -Force; iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))")
              .Run("choco feature enable --name=allowGlobalConfirmation")
              .Run("choco install python3")
              .Copy("Resources/Issue/111/server.py", "C:/")
              .ExposePorts(8000)
              .Command("python", "server.py")
              .Builder().UseContainer().UseImage("mariotoffia/issue111")
              .WaitForProcess("python.exe", (long) TimeSpan.FromSeconds(30).TotalMilliseconds)
              .Builder()
              .Build()
              .Start()

• Added support in TemplateString to distinguish from http(s) URLS and filepaths when doing modifications on windows systems.

• Added IEngineScope to allow for using a certain docker engine within a IDisposable clause. It will switch to the engine choosen
  and switch back (if needed) to the old engine upon Dispose(). This is useful in windows environment where a set of images of both
  Linux and Windows may be executed. An example:

        using (var scope = Fd.EngineScope(EngineScopeType.Windows))
        {
           using(var win = Fd...)
           {
           }
        }

• Fixed bug where WaitForProcess did not work for Windows containers.

• Altered Behaviour on ContainerServiceRemove where it will not Stop() the container unless force = true

• Added support for Pause and Resume (invoke Start again) on both IContainerService´ and ICompositeContainerService`
  and therefore allow for a single docker container or all containers to be paused and resumed. For example:

      using (
        var container =
          Fd.UseContainer()
            .UseImage("postgres:9.6-alpine")
            .ExposePort(40001, 5432)
            .WithEnvironment("POSTGRES_PASSWORD=mysecretpassword")
            .Build()
            .Start())
      {
        AreEqual(ServiceRunningState.Running, container.State);
  
        container.Pause();
        AreEqual(ServiceRunningState.Paused, container.State);
        var config = container.GetConfiguration(true);
        AreEqual(ServiceRunningState.Paused, config.State.ToServiceState());
  
        container.Start();
        AreEqual(ServiceRunningState.Running, container.State);
        config = container.GetConfiguration(true);
        AreEqual(ServiceRunningState.Running, config.State.ToServiceState());
      }

• Added support for netstandard2.1 and therefore works in netcoreapp3.x

• Added ability to keep containers and keeprunning in composite services. Earlier
  those where all killed. For example keep containers (but stop) on dispose may look like this

      var file = Path.Combine(Directory.GetCurrentDirectory(),
        (TemplateString) "Resources/ComposeTests/WordPress/docker-compose.yml");
  
      ICompositeService svc = null;
      IContainerService c1 = null;
      IContainerService c2 = null;
      try
      {
        svc = Fd
          .UseContainer()
          .UseCompose()
          .FromFile(file)
          .RemoveOrphans()
          .KeepContainer()
          .Build().Start();
  
        c1 = svc.Containers.First();
        c2 = svc.Containers.Skip(1).First();
  
        svc.Dispose();
  
        Assert.AreEqual(ServiceRunningState.Stopped, c1.State);
        Assert.AreEqual(ServiceRunningState.Stopped, c2.State);
      }
      finally
      {
        svc?.Dispose();
  
        c1?.Remove(true);
        c2?.Remove(true);
      }