Add jsoncpp as a dependency on Linux packages.

Refs #10821
Plug a gap in scripts not emitting a finished signal.

Refs #10400
Refs #10838. Suppress additional gcc warnings. Fix remaining warning.
Merge branch 'bugfix/10821_linux_pkd_depends_missing_jsoncpp' into develop
Merge branch 'bugfix/10400_script_editor_uneditable' into develop
Merge branch 'feature/10838_suppress_osx_warnings' into develop