2.x Custom decoder not properly handled for parsing configuration properties

[shanman190]

When creating a custom decoder and using the DefaultAppConfig.builder() pattern the custom decoder is ignored when trying to parse the property value.

Example Decoder

import com.netflix.archaius.DefaultDecoder;

import java.time.LocalDate; // Could be Joda LocalDate

public class LocalDateDecoder extends DefaultDecoder
{
    @Override
    @SuppressWarnings("unchecked")
    public <T> T decode(Class<T> type, String encoded)
    {
        if (LocalDate.class.isAssignableFrom(type))
        {
            return (T) LocalDate.parse(encoded);
        }
        return super.decode(type, encoded);
    }
}

Accompanying test case

import com.netflix.archaius.DefaultAppConfig;
import org.junit.Assert;
import org.junit.Test;

import java.time.LocalDate; // Could be Joda LocalDate

public class TestCustomDecoder {
    @Test
    public void testCustomDecoder() {
        DefaultAppConfig config = DefaultAppConfig.builder()
                .withApplicationConfigName("test")
                .withDecoder(new LocalDateDecoder())
                .build();

        config.setProperty("app.date", "2016-01-01");

        Assert.assertEquals(LocalDate.parse("2016-01-01"), config.get(LocalDate.class, "app.date", LocalDate.parse("2015-01-01")));
    }
}

In order to properly decode properties when given a custom decoder in this paradigm, I believe the only change would be to push down the Decoder from the CascadingCompositeConfig into each registered child configuration.