use azure pipelines instead of appveyor for builds

* trial azure pipelines

[skip ci]

* use vs2017

* build pr commits

* include codecov and update test nuget

* add codecov call

* add publish test results step

* include coverlet package for test coverage and allow coverlet dynamic public types

* add azure pipelines badge and remove appveyor badge

* add nuget pack step

* use build configuration variable for nuget pack and move after build

* fix path to package to pack

* change nuget to dotnet pack

* remove old codecov related tools

tools/run opencover.txt

@@ -1,7 +0,0 @@
-src\CodeCoverage\CodeCoverage.cmd
-
-pwd
-
-Expand-Archive tools\Codecov.zip -DestinationPath "tools"
-
-tools\Codecov\codecov.exe -f "src\test-results.xml"