Refactored the code of the am_manager and the authorizers such that when creating a lease, the authorizer will be asked if the caller can create a resource with type "OLease"
Modified the tests such that properties of lease objects will be treated like Time objects instead of Strings.
Simplified the properties mechanism we have. We don't keep the value in temporary variables but we save it as soon as we get a call to set the property. The previous approach is still in the comments but keeping dirty attributes gives us at least one bug. I don't see a reason why not to keep our mechanism simple and straight forward.