* Removed obsolete option: `CLICON_MODULE_LIBRARY_RFC7895'
* Obsolete config options given in the confi file are considered an error
* Added section in CONTRIBUTING relating to optimzation
* Changed reset merge to implicit default values.
* This avoids a potential overwriting of explicitly set default values in the existing config
* Adapted some code to [Make cligen_* functions const ](https://github.com/clicon/cligen/pull/83)
* Test: fixed test for * Fixed: [datamodel tree generated from basemodel tree is not proper when a list has more than one key and key is of enum type](https://github.com/clicon/clixon/issues/417)
