thorium: rename -print-load to -print-thorium-data

This option prints more than just load information.

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium_node: write log file at the end to avoid discarding information

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
message_multiplexer: improve printed information

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: don't print multiplexer information when there are 0 messages

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
message_multiplexer: print node and worker in destroy function

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