Project broken by installing VS2017

[lorenh]

Issue description:

Probably a well known issue already, but it appears that VS 2017 introduced a breaking change that impacts extensions and the way they can no longer use COM references for EnvDTE assemblies.

https://developercommunity.visualstudio.com/content/problem/15434/cannot-find-wrapper-assembly-for-type-library-envd.html

I can't build OpenCover.UI unless I make the reference changes detailed above, as well as marking them to be non-embedded.