Add expanded documentation to AdapterInterface::update

This adds a long description to AdapterInterface::update detailing how the `$where` parameter works

Author: navarr

lib/internal/Magento/Framework/DB/Adapter/AdapterInterface.php

@@ -492,6 +492,13 @@ public function insertForce($table, array $bind);
     /**
      * Updates table rows with specified data based on a WHERE clause.
      *
+     * The $where parameter in this instance can be a single WHERE clause or an array containing a multiple.  In all
+     * instances, a WHERE clause can be a string or an instance of {@see Zend_Db_Expr}.  In the event you use an array,
+     * you may specify the clause as the key and a value to be bound to it as the value. E.g., ['amt > ?' => $amt]
+     *
+     * If the $where parameter is an array of multiple clauses, they will be joined by AND, with each clause wrapped in
+     * parenthesis.  If you wish to use an OR, you must give a single clause that is an instance of {@see Zend_Db_Expr}
+     *
      * @param  mixed        $table The table to update.
      * @param  array        $bind  Column-value pairs.
      * @param  mixed        $where UPDATE WHERE clause(s).