* cppcheck.cpp: Check for JSON error when parsing addon .json files
This fixes that errors in JSON files given via `--addon=*.json` are
silently ignored and maybe only a part of the JSON file is used.
Now the error message which picojson can return is checked and a
corresponding error message is returned again by getAddonInfo().
* naming.json: Fix missing comma
* CLI: Fix naming violations detected by addon naming.py via naming.json
* Addon naming: Add argument for validating names of constants
* LIB: Rename functions/variables so they are valid, loosen naming rules
* GUI: Fix naming violations
Sebastian
Daniel Marjamäki