added tests:
- build and run a .NET 4.5.1 console app
- build crossgen (net451, netcoreapp), skipped because fails atm, logged bug
- build multiple fsproj in same dir (was not possibile with dotnet-compile-fsc)
- add preview2.1 templates
- use .net 1.1 for dotnet-compile-fsc
- use .net core 1.1 in test and dotnet-compile-fsc preview2.1
- in test suite use `dotnet test`+xunit instead of msbuild scripts
- use only nuget.org for build of src/test. use nuget.org + devfeed for running test (temporary)
Enrico Sada