Add support for $BEACOND_HOME environment variable

[camembera]

Add support to beacond for an environment variable to substitute for the --home option. This would likely be in cli/components/client_context.go:

func init() {
	if envHome := os.Getenv("BEACOND_HOME"); envHome != "" {
		DefaultNodeHome = envHome
	} else {
		userHomeDir, err := os.UserHomeDir()
		if err != nil {
			panic(err)
		}
		DefaultNodeHome = filepath.Join(userHomeDir, ".beacond")
	}
}

[wonderfan]

There is --home command flag on the command line. You can override to use your custom home directory if you do not want to use default home directory.