Adding config objects

Here is a first commit. Anyone like to comment before I start on the other directives?

In the case of the accordion there is only one item that can be configured at this stage and so I have kind of hard coded it into the directive.

It occurred to me that often we would have a common pattern of watching the attributes and the config and then merging them when they change.  It seems a good idea to factor out this pattern into a service of it own - maybe $config.  What do you think?