Automate code analysis through Coverity scan

Coverity Scan now supports C# in Beta. Might be interesting to leverage this analysis as part of our CI build.

The project has been registered but isn't fully configured yet.

Some potential references:
 - Travis CI addon: https://scan.coverity.com/travis_ci
 - Manual setup for libgit2: **[coverity.sh](https://github.com/libgit2/libgit2/blob/development/script/coverity.sh)**
 - Interesting **[comment](https://github.com/travis-ci/travis-ci/issues/1975#issuecomment-39793883)** regarding the way to override standard coverity build script