check_es_system

Improving code, fix cert based auth on certain types (fixes #53), code contribution from @jhonny-oliveira in #54

This is a bugfix release and affects a fix for the readonly check type. Before 1.12.1, the readonly check would silently return OK even if the check doesn't work due to missing privileges on the Elasticsearch cluster.

This release contains multiple enhancements:

• Additional authentication method using SSL settings (with key and certificate)
• Additional CPU usage check
• Additional "local" node parameter. Certain checks (cpu, mem, disk, jthreads) can be executed with the additional -L flag.

The base work was submitted in PR #41 . To assure backward compatibility and other improvements, the PR #44 replaced PR 41 and was finally merged.