Define accessors for App's tid, conflict_serial, txn_finished and txn_voted (all in one commit since they are closely related in usage).
Use those accessors instead of accessing properties directly.
Update tests.


git-svn-id: https://svn.erp5.org/repos/neo/branches/prototype3@362 71dcc9de-d417-0410-9af5-da40c76e7ee4