EG/TS: extracted ShutdownHandler from ZP and into Meresco
EG/TS: updated license.
EG/TS: added exitOnError flag to registerShutdownHandler.
TS: busy refactoring and testing processtools's registerShutdownHandler and friends.
TS: more testcoverage for registerShutdownHandler, removed SIGUSR2 persist-but-don't-quit.

Since it used the same observable-message 'handleShutdown'.
TS: fixed test and use exit-status 0 i.s.o. signum.