Configuring the Template Attribute Resolver to consult its dependencies.

[Rod Widdowson]

> The only question was whether to just go ahead and make <Template> required in V4, but I don't think that's going to trip up too
many
> people. 
I cannot see many people wanting an attribute like that, I suppose it might just be useful for automatically combining two
attributes, but its not like we are saying that you cannot continue to do it (and with less typing)


> I think we'll have a 3.4.2 at some point anyway just for other bugs, so there should be some notice of it.

That would certainly help.  

I'll get on to it.