Colorizing the logs are done with an unique function for all possible usages.
Colorization is redone, with more colors used to ease browsing the logs.
Tests are added with the some sample logs.

docker_build, docker_dev_start: give values to VERSION/VERSION_ARG/SENTRY_RELEASE_TAG/SENTRY_RELEASE closer to what the built image value would be

 Allow setting marabunta_db_user and marabunta_db_password in global configuration file and reuse it if set and they are not provided in the command line

Document tox compatibility with 3.7