Associate event definitions with the interfaces they fire at (#387)

* Associate event definitions with the interfaces they fire at as other specs do. Also helps with extracting machine readable data.
* Disambiguate attribute from event for error in IDBRequest

index.bs

@@ -502,12 +502,12 @@ running.
 A [=/connection=]'s [=get the parent=] algorithm returns
 null.
 
-An event with type <dfn event>`versionchange`</dfn> will be fired at an open
+An event with type <dfn event for=IDBDatabase>`versionchange`</dfn> will be fired at an open
 [=/connection=] if an attempt is made to upgrade or delete the
 [=/database=]. This gives the [=/connection=] the opportunity to close
 to allow the upgrade or delete to proceed.
 
-An event with type <dfn event>`close`</dfn> will be fired at a [=/connection=] if the connection is [=/close a database connection|closed=] abnormally.
+An event with type <dfn event for=IDBDatabase>`close`</dfn> will be fired at a [=/connection=] if the connection is [=/close a database connection|closed=] abnormally.
 
 </div>
 
@@ -1137,10 +1137,10 @@ They will return true if any transactions were cleaned up, or false otherwise.
   each [=/transaction=].
 </aside>
 
-An event with type <dfn event>`complete`</dfn> is fired at
+An event with type <dfn event for=IDBTransaction>`complete`</dfn> is fired at
 a [=/transaction=] that has successfully [=transaction/committed=].
 
-An event with type <dfn event>`abort`</dfn> is fired at
+An event with type <dfn event for=IDBTransaction>`abort`</dfn> is fired at
 a [=/transaction=] that has [=transaction/aborted=].
 
 <!-- ============================================================ -->
@@ -1245,12 +1245,12 @@ request=].
 When a request is made, a new [=/request=] is returned with its [=request/done
 flag=] set to false. If a request completes successfully, its [=request/done flag=]
 is set to true, its [=request/result=] is set to the result of the request,
-and an event with type <dfn event>`success`</dfn> is fired at the
+and an event with type <dfn event for=IDBRequest>`success`</dfn> is fired at the
 [=/request=].
 
 If an error occurs while performing the operation, the request's [=request/done flag=]
 is set to true, the request's [=request/error=] is set to the error, and an event with
-type <dfn event>`error`</dfn> is fired at the request.
+type <dfn event for=IDBRequest>`error`</dfn> is fired at the request.
 
 A [=/request=]'s [=get the parent=] algorithm returns the request's
 [=request/transaction=].
@@ -1273,7 +1273,7 @@ A [=/request=]'s [=get the parent=] algorithm returns the request's
 An <dfn>open request</dfn> is a special type of [=/request=] used
 when opening a [=/connection=] or deleting a [=/database=].
 In addition to <a event for=request>`success`</a> and <a event for=request>`error`</a> events,
-<dfn event>`blocked`</dfn> and <dfn event>`upgradeneeded`</dfn> events may be fired at an [=request/open
+<dfn event for=IDBOpenDBRequest>`blocked`</dfn> and <dfn event for=IDBOpenDBRequest>`upgradeneeded`</dfn> events may be fired at an [=request/open
 request=] to indicate progress.
 
 The [=request/source=] of an [=request/open request=]
@@ -2003,7 +2003,7 @@ enum IDBRequestReadyState {
         or `undefined` if the request failed. Throws a
         "{{InvalidStateError}}" {{DOMException}} if the request is still pending.
 
-    : |request| . {{IDBRequest/error}}
+    : |request| . <a attribute for=IDBRequest>error</a>
     ::
         When a request is completed, returns the [=request/error=] (a
         {{DOMException}}), or null if the request succeeded. Throws
@@ -2912,7 +2912,7 @@ and false otherwise.
         If {{IDBObjectStore/put()}} is used, any existing [=object-store/record=]
         with the [=/key=] will be replaced. If {{IDBObjectStore/add()}}
         is used, and if a [=object-store/record=] with the [=/key=] already exists
-        the |request| will fail, with |request|'s {{IDBRequest/error}}
+        the |request| will fail, with |request|'s <a attribute for=IDBRequest>error</a>
         set to a "{{ConstraintError}}" {{DOMException}}.
 
         If successful, |request|'s {{IDBRequest/result}} will be the