thorium: avoid final copy in multiplexer

Link: https://github.com/GeneAssembly/biosal/issues/806
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
genomics: move default coverage value in header

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: in debug mode, display elapsed time for multiplexer

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>