(1) using switch/case on MessageTypeEnum to replace if/else
(2) Bug Fixed: Version, define NULL_VERSION and INIT_VERSION, when
NULL_VERSION is returned (meaning that the key is encountered for the
first time), it will be identified by the client and be replaced by
INIT_VERSION
(3) pid input dialog: using MVC again. model: Configuration (pid); view:
SharePageFragment; controller (PidDialog)