Update loglist for Chrome's new v3 schema

See https://groups.google.com/a/chromium.org/d/msgid/ct-policy/f2958124-f679-406d-8bca-a063b7d37c3an%40chromium.org

loglist/schema.go

@@ -17,6 +17,7 @@ import (
 
 type List struct {
 	Version          string     `json:"version"`
+	LogListTimestamp time.Time  `json:"log_list_timestamp"` // Only present in v3 of schema
 	Operators        []Operator `json:"operators"`
 }
 
@@ -39,6 +40,8 @@ type Log struct {
 		StartInclusive time.Time `json:"start_inclusive"`
 		EndExclusive   time.Time `json:"end_exclusive"`
 	} `json:"temporal_interval"`
+
+	// TODO: add previous_operators
 }
 
 type State struct {