Improved delete clips command logging messages.
Improved delete clips command logging messages.

The command now omits retained counts from log messages when no clips
are retained, and also logs the number of clips deleted per second at
completion.
HaroldMills/Vesper,HaroldMills/Vesper,HaroldMills/Vesper,HaroldMills/Vesper,HaroldMills/Vesper