This pull request adds targeting for .NET Standard 1.5.
It also leaves targeting for .NET Framework 4.6.1 intact which means backwards compatibility.
.csproj files have been updated to new VS2017 syntax. Despite of backwards compatibility of library, new VS2017 will be needed to build.
Sample projects have been updated to new .csproj syntax too.
Sample projects will build into single shared Samples/bin/ directory
Minor code fixes to make it compatible with .NET Standard 1.5, but no behaviour has been changed. You can easily review what have been changed in separate commits.
Samples/bin/directory