Previously, the number of processes spawned was always
QThread::idealThreadCount() (returning the number of logical CPU
cores). On new systems with many cores, however, this can result
in 12, 16, 24, or ... processes being spawned, which is a bit
excessive.
This establishes a new config variable,
'max_numprocs_tagclients' within the Settings group, in order
to limit the maximum number of tag client processes that get
spawned. It also adds a means of setting this via the Behavior
page in Settings. It can be set to any integer in the interval
[1, QThread::idealThreadCount()]; it defaults to the maximal value
so as to emulate the old behavior.