.NET Standard

.Net Standard (#15)

* remove obsolete file

* convert project to .net standard

* styleop update

* revert (supported in standard 1.5)

* remove gitlink

* xunit, stylecop, specflow

* fix usages of scenario context

* dotnet xunit

* use choco opencover on appveyor

* opecover dotnet.exe path

* fix path fix

* -oldstyle codecov

* full pdbs required by codecov

* ps exit code

* xunit -noshadow

* cake to test

* no need for opencover in appveyor

* fix build of docu.csproj

* fail if tests fail

* indent fix

* brig back stylecop settings for codefactor.io

* try to make open cover fail the build

* fix null return

* added gitlink to cake

* add gitlink to appveyor

* move all build scripts to cake

* fix appveyor cake script

* fix cake params

* haave gitversion update build number

* gitverions prerelease

* twaek gitversion task when on CI

* no need twice

* temporary workaround for context resolver

* fix test

* split tests in context readme

* typo and test for both method and property