Release 1.0.0-alpha10

Release .NET Functions Framework 1.0.0-alpha10

Changes since 1.0.0-alpha09:

- Update Google.Events and Google.Events.Protobuf to 1.0.0-alpha05
- Add more convenience methods in FunctionTestBase
- Update handling of Firestore CloudEvent conversion of source/subject
- Fix #126: Source URIs beginning with "//" are now not converted to "file://"