Update Scenarioo-CS Docu and NuGet Account / Package Description

[bruderol]

I think our Scenarioo-CS docu and NuGet Acocunt would need a little bit of love.

Issues to be solved:

• Outdated links in C# docu: see also PR Update Links in Docu #15

• C# docu should also link to our overal docu - e.g. this specific page that might be of interest: http://scenarioo.org/docs/master/tutorial/How-to-use-Scenarioo-Writer-Library.html and maybe to the examples listed here: http://scenarioo.org/docs/master/examples.html

• Outdated links on this page here: https://www.nuget.org/packages/Scenarioo-cs/

• Also some explanations on the NuGet package page are not anymore accurate (we talk of a "Scenarioo Writer" and not "Scenarioo API" anymore).

• We should avoid using Wikis and only link to MD files on our master branch ---> easier to update on new releases and versioned with the software.

@tobiaszuercher I started to do it, but it seems not to be so easy, so I had to stop ... maybe Metadata can only be changed with a new release? Linking the README.md from master branch into NuGet might be a good option? We do the same for npm here:
https://www.npmjs.com/package/scenarioo-js

Or what do you think?
In any case we should also update our README.md first!

What I already did: I migrated our nuget account to a Microsoft account for Scenarioo - since nuget accounts are deprecated - see Emails.