[doclint] add linting for class properties

This patch:
- adds linting for class properties
- adds documentation for the missing class properties

References #14.

lib/NetworkManager.js

@@ -291,7 +291,6 @@ class Request extends Body {
     this.url = payload.url;
     this.method = payload.method;
     this.headers = Headers.fromPayload(payload.headers);
-    this.postData = payload.postData;
   }
 
   /**