Add extension methods for registering the SQL durability provider

[cgillum]

Resolves #30

This PR adds an extension method to register the Durable Task SQL storage provider for Azure Functions (and Azure Web Jobs).

Here is an example of how we register the SQL provider in our integration tests.

this.functionsHost = new HostBuilder()
    .ConfigureLogging(
        loggingBuilder =>
        {
            loggingBuilder.AddProvider(this.logProvider);
            loggingBuilder.SetMinimumLevel(LogLevel.Information);
        })
    .ConfigureWebJobs(
        webJobsBuilder =>
        {
            webJobsBuilder.AddDurableTask(options =>
            {
                options.StorageProvider["type"] = "mssql";
            });
        })
    .ConfigureServices(
        services =>
        {
            services.AddSingleton<INameResolver>(this.settingsResolver);
            services.AddSingleton<IConnectionStringResolver>(this.settingsResolver);
            services.AddSingleton<ITypeLocator>(this.typeLocator);
            services.AddDurableTaskSqlProvider();
        })
    .Build();

Also in this PR:

• Increment version to v0.9.1-beta
• Update dependencies
• Minor doc updates