WSE is always packaged, at a minimum with AVC. that combination on an ASA is all the licensing you need to block web applications per user. You will of course need to implement a scheme to identify your users in order to use their identity in a policy. That can be via local database (seldom used as it doesn't scale well) or via integration with your Microsoft AD infrastructure (via active authentication or optionally using the free Context Directory Agent (CDA) server running on a VM in your environment) or via something like the Identity Services Engine (ISE - a licensed product).
