Refactor crypto initialsync handling

Pass a store into the Crypto object so that it doesn't need to make assumptions
about the EventEmitter, and use the new metadata on sync events to distinguish
between initialsyncs and normal syncs

src/client.js

@@ -158,6 +158,7 @@ function MatrixClient(opts) {
             this, this,
             opts.sessionStore,
             userId, this.deviceId,
+            this.store,
         );
 
         this.olmVersion = Crypto.getOlmVersion();