TSSS db cleanup throttle

In the Statistics Services the default db.cleanup.run.interval.minutes property is 0 (The default value of 0 specifies that the Spotfire Statistics Services job queue database should grow indefinitely.)  This means that the database and lots of files keep growing.  After a long time, it then becomes obvious something does not cleanup.  By this time there can be hundreds of files and Gb's of data.

When setting this value to say 1400 (24 hours), the server then struggles to catch up on the cleanup, because its other default db.cleanup.time.to.live.days is set to keep only 7 days worth of data.  In some cases the system cannot perform this cleanup because it needs even more disk space to generate the task list.

I propose a third property, db.cleanup.throttle with a default value of 100.  This limits the number of entries to cleanup each run. Thus limiting any system strain.

This property will need to be adjusted by the admin, if more than this number of jobs comes in on average within the cleanup interval time.