indexer: update and fix documentation

lib/indexer/addrindexer.js

@@ -1,5 +1,5 @@
 /*!
- * addrindexer.js - addr indexer
+ * addrindexer.js - address indexer for bcoin
  * Copyright (c) 2018, the bcoin developers (MIT License).
  * https://github.com/bcoin-org/bcoin
  */

lib/indexer/indexer.js

@@ -1,5 +1,5 @@
 /*!
- * indexer.js - storage for indexes
+ * indexer.js - abstract interface for bcoin indexers
  * Copyright (c) 2018, the bcoin developers (MIT License).
  * https://github.com/bcoin-org/bcoin
  */
@@ -21,11 +21,12 @@ const {ZERO_HASH} = require('../protocol/consensus');
 
 /**
  * Indexer
+ * The class which indexers inherit from and implement the
+ * `indexBlock` and `unindexBlock` methods and database
+ * and storage initialization for indexing blocks.
  * @alias module:indexer.Indexer
  * @extends EventEmitter
- * @property {IndexerDB} db
+ * @abstract
- * @property {Number} height
- * @emits Indexer#chain tip
  */
 
 class Indexer extends EventEmitter {
@@ -121,7 +122,7 @@ class Indexer extends EventEmitter {
   }
 
   /**
-   * Close the indexdb, wait for the database to close.
+   * Close the indexer, wait for the database to close.
    * @returns {Promise}
    */
 

lib/indexer/txindexer.js

@@ -1,5 +1,5 @@
 /*!
- * txindexer.js - tx indexer
+ * txindexer.js - transaction indexer for bcoin
  * Copyright (c) 2018, the bcoin developers (MIT License).
  * https://github.com/bcoin-org/bcoin
  */