Fix #358, Add native permissive mode configuration

[skliper]

Describe the contribution
This adds the native_osconfig.h which is included after
the default_osconfig.h if SIMULATION=native is set.
Fix #358

Testing performed
Steps taken to test the contribution:

1. copy cfe/cmake/sample_defs to top dir (per standard setup instructions)
2. make SIMULATION=native prep
3. make; make install;
4. Execute core-cpu1 in build/exe/cpu1 and confirmed permissive mode
5. Also did steps above with just make prep, and confirmed permissive mode wasn't set

Expected behavior changes
No longer requires sed "hack" to change the setting in default_config.h

System(s) tested on

• Hardware: cFS Dev server 2
• OS: Ubuntu 18.04
• Versions: master bundle with this branch

Additional context
Update related README's and CI to no longer perform sed "hack"

Third party code
N/A

Contributor Info - All information REQUIRED for consideration of pull request
Jacob Hageman - NASA/GSFC

[skliper]

Eliminated duplicate documentation of the define.

[astrogeco]

CCB 20200226 - Approved