WFLY-2774 Non-distributed, stateful web applications cannot be load balanced using sticky sessions

https://issues.jboss.org/browse/WFLY-2774
https://issues.jboss.org/browse/WFLY-2853

Implements session routing in Undertow via a SessionConfigWrapper.  Create SessionIdentifierCodec abstraction that is responsible for encoding/decoding the session identifier.  Distributable SessionIdentifierCodec implementation uses a RouteLocator, which has been decoupled from the SessionManager in org.wildfly.clustering.web modules.

Added default value for instance-id (i.e. ${jboss.node.name}) to Undertow subsystem.

Add integration tests that validate session routing for both distributable and non-distributable web applications.