Project Management API (#228)

*  Implement more methods of the FirebaseManagementService; refactoring. (#214)

Implement list_android_apps and create_android_app; perform some refactoring on RPC-making code. With these two methods implemented, an integration test has been written at this time as well.

* Complete Implementation of the project_management Module

Implementation of all client-level functionalities (both Android and iOS), making use of the newly published Firebase Management API.

* Add an (incomplete) unit test for package_management; add a MockMultiRequestAdapter test utility (#218)

* Add the bulk of the remaining unit tests for the project_management module (#219)

* Complete implementation and unit tests (#223)

* Add TestListAndroidApps

* Fix the maximum page size.

* Fix string formatting.

* Fix the naming of updateMask to be consistent with precedent.

* Implement __eq__ and __hash__ for ShaCertificate

* Add remaining unit tests.

* Fix a subtle Python 2.7 vs 3 compatibility problem.

* Rework the version compatibility line to be more elegant. Introduce the same thing to unit tests.

* Addressing reviewer comments.

* Fix a subtle Python 2.7 vs 3 compatibility problem.

* Fix lint

* Fix lint

* Addressing reviewer comment.

* Add __eq__ and __hash__ methods to AndroidAppMetadata and IosAppMetadata; write the remaining unit tests.

* Small alterations to __eq__ implementations.

* Addressing reviewer comments.

* Addressing reviewer comments.

* Porting reviewer comments to this branch.

* Inlining more constants

* Using a stronger assertion for an empty request body.

* Remove the name attribute from AndroidAppMetadata and IosAppMetadata as per offline discussion.

* Address reviewer comments.

* Fix unit tests that triggered __ne__ with flipped arguments instead of __eq__.

* Implement __ne__.

* Use testutils.run_without_project_id

* Updated changelog

* Minor docs formatting fix

Author: hiranya911

CHANGELOG.md

@@ -1,8 +1,10 @@
 # Unreleased
 
+- [added] A new `project_management` API for managing apps in a
+  project.
+- [added] `messaging.AndroidNotification`type now supports channel_id.
 - [fixed] FCM errors sent by the back-end now include more details
   that are helpful when debugging problems.
-- [added] `messaging.AndroidNotification` type now supports `channel_id`.
 - [fixed] Fixing error handling in FCM. The SDK now checks the key
   type.googleapis.com/google.firebase.fcm.v1.FcmError to set error code.
 - [fixed] Ensuring that `UserRecord.tokens_valid_after_time` always