Release 1.0.0-alpha03

Changes since 1.0.0-alpha02:

- Use ASP.NET Core dependency injection to create function instances
- Add dependency injection attributes and types for custom dependency injection
- The JSON logger now uses "category" instead of "log_name"
- New methods in EntryPoint to enable integration testing
- New package of Google.Cloud.Functions.Invoker.Testing for simpler integration testing support
- On start-up, log the detected function type
- Templates updated to use Microsoft.NET.Sdk instead of Microsoft.NET.Sdk.Web (to avoid Visual Studio adding confusing launch settings)
- Added VB and F# templates