Allowed injections to be inherited by deriving attributes

[pamidur]

This PR allows injections to be inherited.

so you can do something like:

    [Injection(typeof(CacheAspect), Inherited=true)]
    public abstract class CacheAttribute : Attribute
    {
        public abstract ObjectCache Cache { get; }
        public abstract CacheItemPolicy Policy { get; }
    }

    public class MemoryCacheAttribute : CacheAttribute
    {
         ... implementation
    }

And then MemoryCacheAttribute will behave as if it has [Injection(typeof(CacheAspect))]