Login, Logout. Service Call Authentication

LL-3: Session ID can be used to authenticate users with active sessions
on successive service class after login.  Logout method added which
closes DB connection and removes sessionid/connection map from
SessionTracking.  SessionTracking structure now Hashtable-based for
thread safety.  Error handling edited to respond appropriately to
server/user errors.

InsertTest and Logout currently accept sessionid as a header in REST
call.