add connection manager
update dispatch in configHelper
add release from connection
add thread-safe
debug error caused by thread
add timeout.
fix concurrent bug.
add restart vm mechanism.
fine tune.
Merge branch 'master' of https://github.com/zkoss/ztl into parallel-improve
remote log for performance
remote log
fine tune
add log
bug fix
add log
add log
add log
add log
add log
bug fix
bug fix