The cnetedit application has been refactored to be callable; Makefile tests...

The cnetedit application has been refactored to be callable; Makefile tests have been removed and replaced by gtests (#5348)

* The cnetedit application has been refactored to be callable; Makefile tests have been migrated to gtest format. Addresses #5346.

* Removed extraneous variables from FunctionalTestsCnetedit.cpp. Addresses #5346.

* Updated gtests; replace cubes with labels. Addresses #5346.

* Per review cleaned up sloppy spacing; made global variables static in cnetedit.cpp to avoid issues when linking libisis. Addresses #5346.