Release 6.20.2: Extended monitoring with amount of sessions in each container

[changerequest]

The output of showruntimestats is extended with 2 new values. This values are written if the short option '-i' or the long option '--sessionstats' is provided. The values contain the session container sizes as arrays:

com.openexchange.sessiond:name=SessionD Toolkit,NumberOfLongTermSessions = [0, 0, 0, 0, 0, 0, 0, 0, 0]
com.openexchange.sessiond:name=SessionD Toolkit,NumberOfShortTermSessions = [0, 0, 0, 0, 0, 1, 0, 0, 0, 0]