add API viewer, mv repl subcommand to api (#41)

pkg/cfg/config.go

@@ -107,6 +107,8 @@ type Config struct {
 	MaxAge                              string
 	MaxDocs, MaxShardSize, MaxShardDocs int  // roll over
 	DryRun                              bool // rollover: -n
+
+	Tag string // api ls: -t
 }
 
 func NewConfig() *Config {