exported IConsole and ILog from Autofac to MEF Extensions

Autofac does not automatically export components to MEF extensions - it needs to be specified explicitly.

Sine we'd like to give script pack authors ability to use `ILog` and `IConsole` in the script packs, added explicit export of these two interfaces.

You can now do this as a script pack author:

    public class TestContext : IScriptPackContext
    {
        private readonly ILog _logger;
        private readonly IConsole _console;

        public TestContext(ILog logger, IConsole console)
        {
            _logger = logger;
            _console = console;
        }

        public void Hello()
        {
            _logger.Info("Writing hello!");
            _console.WriteLine("Hello");
        }
    }

    public class TestPack : ScriptPack<TestContext>
    {
        [ImportingConstructor]
        public TestPack(ILog logger, IConsole console)
        {
            Context = new TestContext(logger, console);
        }
    }