[ADD] openerp.tools.func.lazy_property():

 Decorator for a lazy property of an object, i.e., an object attribute
 that is determined by the result of a method call evaluated once. To
 reevaluate the property, simply delete the attribute on the object, and
 get it again.
[FIX] http: nodb_routing_map become a lazy property. load_addons() is also lazy called