pulsecounter: bugfix + unittests
channel unit test added

added unit test for LSC, non-blocking, read from empty  - should throw
DataNotAvailable
LSMNothing removed, LSC can now be closed

previously LSC did not differ between close/failed and close/OK. It does
now
added enable, disable for counters
instrumentation: exception names refactored
added snapshots and monitors
monitor API refactored
InstrumentationManager now a monitor
docstring for InstrumentationManager fixed
docstring for Monitor
added remove_counter for InstrumentationManager
added delta counter
network removed; use channels instead
exception formatter added
added displaying globals for exc_formatter
superior mechanism to exc_formatter added
unit test for Trackback
Trackback code compacted
__slots__ for Traceback classes
unittest listing updated