Various EAS related changes related to accounts and services.

* Renamed ISyncManager/ISyncManagerCallback to IEmailService/IEmailServiceCallback
* Restored ExchangeTransportExample to its original state; created ExchangeStore to
  handle validation functionality instead; updated stores.xml to reflect these changes.
* Add support for AccountManager in EAS code (this is necessary for the contacts and
  calendar providers to work with syncable data); created EasAuthenticatorService to
  as our authenticator, which required adding authenticator.xml and modifying the
  manifest to register our service with AccountManager metadata
* Created EmailServiceProxy as a convenience for the UI in calling into the EAS
  service; created EmailServiceStatus class for status codes in callbacks.
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 21d18eb..a49bfba 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -178,6 +178,16 @@
             android:enabled="true"
             >
         </service>
+
+        <!--Required stanza to register the EasAuthenticatorService with AccountManager -->
+        <service android:name=".service.EasAuthenticatorService" android:exported="true">
+            <intent-filter>
+                <action android:name="android.accounts.AccountAuthenticator" />
+            </intent-filter>
+            <meta-data android:name="android.accounts.AccountAuthenticator"
+                       android:resource="@xml/authenticator" />
+        </service>
+
         <provider
             android:name=".provider.AttachmentProvider"
             android:authorities="com.android.email.attachmentprovider"