Review how Permission Manager handle dynamic namespaces

[luigibarbato]

In the last implementation of Permission Manager, it assumed that various resources were created and managed solely in its own "permission-manager" namespace (#137). In fact, the namespace was hardcoded during the creation of the ServiceAccount and RoleBinding. Currently, we have found a workaround to this limitation by using the namespace of the current kube context. This of course can only be a temporary change and so we will have to investigate a more robust solution.