2.0.39

Linux support in ci (#16)

* extended output on failed verapdf execution

* fixed error message creation code

* fixed linux testsetup

* nonfunctional changes

* dropped things that didnt do anything

* dropped unused variable

* Added notes about dependencies

* Moved forward to async implementation,
Fixed some compile warnings

* Updated ubuntu 20.04 cook book

* Major version increased

* Added integrative test

* Enabled dependency injection in webapp

* upgraded nuget references