[development] D6 Cleaning up on module uninstall

[jeff at ayendesigns.com]

So, looking at other modules that have content types, it seems that when 
they uninstall they do a content_notify with uninstall as the action. 
When I do this, everything indicates a clean uninstall otherwise, but 
nothing really seems to change regarding the cck info, in that the field 
table, content type table and entry in node_type all remain. Is this 
right? It certainly complicates the install logic in that even though 
it's my content type and field, I can't assume that they don't exist 
when I install.