Reduce/configure logging verbosity

[jamespeapen]

A lot of messages are printed very fast when running on all chromosomes or many cells that can't really be read.
Could use spdlog to control logging level or reduce the calls to message, looking for cases where whats true of one sample/chromosome is probably true for all of them.

[biobenkj]

I'm perfectly fine modifying the logging capacity if that is needed when running on all chromosomes. The current rapid fire messaging was for debugging and also for others working on the code in previous iterations to see what was happening and what might be bottlenecks based on visual inspection of logging output. Bottom line - feel free to modify logging or decrease verbosity in the current iteration.

[jamespeapen]

Could use pbapply to show progress/current iteration info so there's signs of life on long-running computations.