Add Java 8 / lambda friendly helper for CacheLoader

Almost every usage of CacheLoader only needs to implement load(), so being able to do that with a lambda would be helpful. Something like this:

public static <K, V> CacheLoader<K, V> cacheLoader(LoaderFunction<K, V> loader)
{
    return new CacheLoader<K, V>()
    {
        @Override
        public V load(K key)
                throws Exception
        {
            return loader.load(key);
        }
    };
}

public interface LoaderFunction<K, V>
{
    V load(K key)
            throws Exception;
}

[lowasser]

Note there already is this for a bare Function: https://google.github.io/guava/releases/22.0/api/docs/com/google/common/cache/CacheLoader.html#from-com.google.common.base.Function-

[ben-manes]

Well, perhaps consider Caffeine.newBuilder().build(key -> ...)? https://github.com/ben-manes/caffeine