Introduced RegisterValueType<TValueType>() method

[HakamFostok]

• Introduced RegisterValueType<TValueType>() method to allow custom value type registration using generics
  which is just a wrapper for the RegisterValueType(Type type) method

• Use ArgumentNullException.ThrowIfNull instead of throw manually

[HakamFostok]

Thanks for approving. I have a question about the process.
As my PR has been approved, why has it not been merged yet?
Is there a merge window before releasing a new version, and all the merges happen at that window?
Thank you

[jeremydmiller]

"As my PR has been approved, why has it not been merged yet?" --

Hey, thanks for doing this, but it's at most a convenience thing, and I'm just now working on the next round of clean up. I won't say that we have any formal process or timing, but if you'll look at our release cadence on Nuget, you'll notice that we're releasing all the damn time and certainly faster than most OSS projects of any level of complexity.

[HakamFostok]

Thanks a lot, I really appreciate it, I just wanted to make sure that everything was ok and I'm not missing anything.
I am very glad that you mentioned cleaning up, because on Sunday, I was preparing about 8 PRs just for cleaning.
I will be very happy to share them and try to help in making Marten better.
I am using it in my 2 projects, and I hope that people know about it more and embrace the Event-sourcing mindset more and more.
Thanks again for making this library and I will be starting to sent some more PRs to make Marten better and better.
Thanks again