Add support for <long> nodes

[cmandlbaur]

Add support for the UseLong flag to optionally use <long> nodes instead of <i8> nodes.

Added tests where it seemed to make sense.

Fixed a couple of typos in the README

[cmandlbaur]

@LordVeovis it would be great if this could be included.

It's not really per the xmlrpc spec, but then neither was the i8 node.

It looks like the build failed to sign because of a login issue.

[LordVeovis]

Hey,

I saw your email, I am sorry for not responding here. Currently I do not have Internet at home so... I am not checking here very often as I do not use github at work.
On the paper it looks good.
For now, I have fixing CircleCI pieline and upgraded the project to something supported (.netcore3.1 -> .net 8.0) in the dev-circleci branch. So far so good and I hope to run your code with this base this week. If the tests are green, that should be enough.

So next steps:

1. I run the tests locally
2. If green, I merge dev-circleci on master
3. After the fix, merge it.

Please ignore the Codacy issue.

[cmandlbaur]

Thank you!

[LordVeovis]

1.3.1 released!