add pre build hooks for .default files

[armageddon421]

The goal of this issue is to replace the config files in data/cfg with *.default files outside of the data directory. A pre-build hook shall be used to copy the *.default files to their appropriate location before the build. The data/cfg directory is to be added to the .gitignore file. This makes development/deployment easier because config files should not make the environment "dirty".

https://docs.platformio.org/en/latest/projectconf/advanced_scripting.html#before-pre-and-after-post-actions