Cics GETNEXT improvements

[mm-broadcom]

Implementation of the GETNEXT command from the IBM documentation.

How Has This Been Tested?

Wrote tests to verify the various commands based upon the documentation given by IBM.

Checklist:

• [x] Each of my commits contains one meaningful change
• [x] I have performed rebase of my branch on top of the development
• [x] I have performed a self-review of my own code
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] I have checked my code and corrected any misspellings