Add convenience method for parsing LogLevel values form string.

src/log-message.ts

@@ -9,6 +9,17 @@ export enum LogLevel {
   FATAL
 }
 
+const kv = 'WARN';
+const TEST = LogLevel[kv];
+
+export function parseLogLevel(str: string, defaultLevel = LogLevel.INFO): LogLevel {
+  if (Object.prototype.hasOwnProperty.call(LogLevel, str)) {
+    return LogLevel[<any>str] as unknown as LogLevel;
+  } else {
+    return defaultLevel;
+  }
+}
+
 export interface LogMessage {
   scope: string;
   level: LogLevel;