Revision 273434

Added a callback for setProperty. This would allow different property
stores to implement their own policy.

This feature will not work in ant15 ( for now ).

Also changed Project to Object - and use it as a context. This makes
the callback more generic and the hooks less dependent of ant.

The only major issue on dynamic properties for me is the JNDI stuff.
I think the Context interface could be a better abstraction, but
on the other side it is much more complex. I also want to finalize
the JNDI property source and abstract the properties via JNDI
so tasks can be created without any dep on ant, but still accessing
properties and refs.