Akka.Streams.TestKit 1.3.7

Maintenance Release for Akka.NET 1.3** Akka.NET v1.3.7 is a minor patch consisting mostly of bug fixes. DotNetty stabilization** We've had a number of issues related to DotNetty issues over recent weeks, and we've resolved those in this patch by doing the following: [Locking down the version of DotNetty to v0.4.6 until further notice](https://github.com/akkadotnet/akka.net/pull/3410) [Resolving memory leaks introduced with DotNetty in v1.3.6](https://github.com/akkadotnet/akka.net/pull/3436) We will be upgrading to DotNetty v0.4.8 in a near future release, but in the meantime this patch fixes critical issues introduced in v1.3.6. Bugfixes** 1. [Akka.Persistence.Sql: Slow reading of big snapshots](https://github.com/akkadotnet/akka.net/issues/3422) - this will require a recompilation of all Akka.Persistence.Sql-type Akka.Persistence plugins. 2. [Akka.Fsharp: spawning an actor results in Exception in 1.3.6 release](https://github.com/akkadotnet/akka.net/issues/3402) See [the full list of fixes for Akka.NET v1.3.7 here](https://github.com/akkadotnet/akka.net/milestone/25). | COMMITS | LOC+ | LOC- | AUTHOR | | --- | --- | --- | --- | | 5 | 130 | 180 | Aaron Stannard | | 3 | 7 | 1 | chrisjhoare | | 2 | 3 | 1 | ivog | | 1 | 70 | 17 | TietoOliverKurowski | | 1 | 41 | 4 | Bart de Boer | | 1 | 11 | 3 | Oleksandr Bogomaz | | 1 | 1 | 1 | Vasily Kirichenko |