Fix defect where Execution would re-create/register it's counters and have them not be visible.   Basically, Instrumentation ion Add now just accepts the last counter registered with a given name.
Avoid NPE if user enters bad name for elements.
Increase upper limit on UpdateInterval (so I can play Giz's new stuff).
No functional change - just a change on the upper bound on the control.
Keep serial port Open execption from propagating (which cause problems later).
Ebrady on doityourselfchristmas reported a problem cancelling out of the SSF.  When I loaded the config on my system (which doesn't have COM1, the serial port Open throws in the device Start.  This primed things to fail when the device was eventually Stopped.  Ebrady was cancelling out of SFF which reloads system config (stopping and stating all devices).  Stopping the device failed because Start never completed successfully.  This change keeps the Open exception from propagating, thus preserving the ability to Stop sussessfully - no more crash.

BTW, eventually we probably want to guard any call downs to device handlers so that the core/base classes can preserve the invariants they count on.  But this localized fix seems to move the ball forward at least in this case.