Updates for the pid caching. By default it is still switched off

Updates for the pid caching. By default it is still switched off
and can be switched on by a parameter in the AddTask macro
(AddTaskPIDResponse.C).
From a small test I got about 8% less cpu time and 5% less real time
if the caching is switched on.
However this of course completely depends on how often the pid values are
requested for a track. The less it is needed, the less the gain, of course.
Jens Wiechula