Provide option for conda installation parameters

[H4dr1en]

First, thanks for the great work 👍

Currently, agents with package_manager.type = conda will install silently using --quiet:

Executing Conda: /home/h4dr1en/miniconda3/bin/conda install -p /home/h4dr1en/.trains/venvs-builds/3.6 -c defaults -c conda-forge -c pytorch pip==20.1 --quiet --json

For debugging purposes, it would be great if instead one could specify other parameters acceptable by conda install, notably -v

[bmartinn]

@H4dr1en that sounds like a good idea, there is already a --debug flag, but it will not output the conda results to screen. Should not be a problem to add :) btw: --quiet --json will just remove the upgrade banner, the actual full return results are in the json format, so just printing it out should give you an insight on what's going on.