Implement continous integration

We should have a minimum set of continious integration.
As a first step I implemented some build scripts based on fake.
Currently the build does:
* Install dependencies for the build with paket
* Install nuget dependenices of the Solution
* Get the version with GitVersion and path AssemblyInfo
* Build
* NuGet pack
* If the build was triggered by a git tag, the package is published to NuGet.org