Look for `OPENTAP_COLOR` variable to enable colors without having to use `--color` on every command

Valid values for this environment variable should be:

• always just always use colors (same as --color on all tap commands)
• auto use color except when output is redirected (e.g. tap package list -i > installedPackages.txt or VERSION="$(./tap sdk gitversion)")
• never don't use color (same as not setting the variable)