Add configurable interval display of processed records for loader

The following log entry is an example of a hard-coded interval of 500 entries processed for loader jobs. Could we please make this configurable and default it to 500? I will likely make mine 1000 or 2000 reduce noise in logging.

daemon_1_cce6a97783aa | 2019-03-13T00:50:03.165214629Z grouper-api;grouper_error.log;grouper_dev;daemon;2019-03-12 20:50:03,164: [pool-1-thread-343] INFO GrouperLoaderType.syncOneGroupMembership(2886) - - App:ARS:Roles:UF_SS_USER processed 19000 records, finding new members to remove, 19000 of 234435 subjects