[ENH] Local condarc

[AlbertDeFusco]

This has been mentioned in other PRs or issues. It could be useful for a project to store its own .condarc file. In order for it be respected anaconda-project would just need to set $CONDARC to the project path if the file is found.

https://docs.conda.io/projects/conda/en/latest/user-guide/configuration/use-condarc.html#searching-for-condarc

You'll see in the precedence that the $CONDARC settings are applied/merged after the other config files, but can still be overridden if needed