thorium_actor: disable log level LOG_LEVEL_DEFAULT by default

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
unitig_visitor: by default, nothing is logged

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: use THORIUM_ENABLE_LOG_LEVEL and THORIUM_DISABLE_LOG_LEVEL

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
documentation: add thorium_actor_log in documentation

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

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: don't print new line twice

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

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

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