all: disable log message colors outside of geth

Also tweak behaviour so colors are only enabled when stderr is a terminal.

cmd/evm/main.go

@@ -112,7 +112,7 @@ func init() {
 }
 
 func run(ctx *cli.Context) error {
-	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat()))
+	glogger := log.NewGlogHandler(log.StreamHandler(os.Stderr, log.TerminalFormat(false)))
 	glogger.Verbosity(log.Lvl(ctx.GlobalInt(VerbosityFlag.Name)))
 	log.Root().SetHandler(glogger)