Mono support

*revert .fsproj files from VS2013 to VS2012 while xBuild isn't fixed
*update to latest NuGet which solves the trailing space problem and doesn't require the consent envvar to be set
*disable silverlight and portable versions on mono
*add mono compiler path for documentation tests
*fix build.fsx and build.sh
Update WorldBank tests
Merge pull request #211 from ovatsus/master

Mono support