Add .ruleset file for Code Analysis

[Arithmomaniac]

We now have coding standards, but not everything can be configured in editorconfig. Some things still have to be configured in rulesets.

We should create a rulesets file and add a reference to it in the global .props file so that all projects are bound to it.

If some rules that we would like are missing, we can add StyleCop Analyzers as a development-only dependency.

(follows-up #18 and #111)

[KalinaTSD]

I believe StyleCop will be useful for our common work. I'm going to include this in the solution.