Fix CPU Utilization Call and host_config Script

[afholman]

Initial fixup for both Nagios Core and XI that includes the following changes:

• Add additional build directories to .gitignore.
• Clean up typos in the READMEs.
• Fix the CPU Utilization call to correctly retrieve the CPU utilization instead of just 0%. (https://github.com/IBM/nagios-for-i/issues/41)
• Update jt400.jar file to 20.0.7 (built with java 8 from https://github.com/IBM/JTOpen/releases)
• Fix host_config shell script in libexec to include jt400.jar file in the class path. Without this update it doesn't work for Nagios Core. (https://github.com/IBM/nagios-for-i/issues/40)

All changes have been tested in my own Nagios Core and Nagios XI environments. Everything seems to work for me, but any additional testing is welcome since there wasn't any information left behind on how to build/package the project.

Note: All the "force-pushed" logs were done to add in the DCO signings.

[afholman]

Code has been reviewed and tested in a different environment than my own. Merging changes.