cascade plugin

[GoogleCodeExporter]

create a plugin that simplifies the configuration of create and delete cascades.

i.e., it should be as simple as possible to say, e.g., 

* when a member of collection /foo is created, a new member of collection /bar 
should also be created as a side-effect, and the two members linked via a 
certain rel/rev; 

* when a member of collection /foo is created, then a new collection at 
/bar/$id should be created as a side-effect, and the member and collection 
linked via a certain rel/rev

* when a member of collection /foo is deleted, then any member linked via the 
'bar' link relation should also be deleted as a side-effect

* when a member of collection /foo is deleted, then any collection linked via 
the 'bar' link relation should also be deleted as a side-effect

...

Original issue reported on code.google.com by alimanfoo@googlemail.com on 28 Feb 2011 at 9:04