Make the templates compatible for FSharp.AutoComplete with VS2015 tooling

[Vaub]

Hello,

I had problems using the FSharp generator (or generating a .fsproj from VS/Xamarin) and Ionide on my Windows machine (no problem on OS X) both with VS Code and Atom (also with the Vim integration). FSharp.Autocomplete (for some reason, normal msbuild had no problems) could not process .fsproj files when using VS2015 since the targets checked for 2013.

Updated the templates. I ONLY tested manually the Console and the Class Library using http://yeoman.io/authoring/ instructions. I'm not sure how Yeoman works so maybe there's a better way.

Having fun so far with learning F#, but it seems that VS2015 is not well supported by many F# tooling.

If someone is interested, here's what FSharp.AutoComplete says without this condition:

{
    "Kind" : "project",
    "Data" : {
        "Project" : "d:\\Development\\fsharp\\sample\\sample.fsproj",
        "Files" : [],
        "Output" : "null",
        "References" : ["C:\\Program Files (x86)\\Reference Assemblies\\Microsoft\\FSharp\\.NETFramework\\v4.0\\4.4.0.0\\FSharp.Core.dll"],
        "Logs" : {
            "d:\\Development\\fsharp\\sample\\sample.fsproj" : "Microsoft.Build.Exceptions.InvalidProjectFileException: The value \"\" of the \"Project\" attribute in element <Import> is invalid. Parameter \"path\" cannot have zero length.  d:\\Development\\fsharp\\sample\\sample.fsproj\r\n   at Microsoft.Build.Shared.ProjectErrorUtilities.ThrowInvalidProject(String errorSubCategoryResourceName, IElementLocation elementLocation, String resourceName, Object[] args)\r\n   at Microsoft.Build.Shared.ProjectErrorUtilities.VerifyThrowInvalidProject(Boolean condition, String errorSubCategoryResourceName, IElementLocation elementLocation, String resourceName, Object arg0, Object arg1, Object arg2, Object arg3)\r\n   at Microsoft.Build.Evaluation.Evaluator`4.ExpandAndLoadImports(String directoryOfImportingFile, String importExpressionEscaped, ProjectImportElement importElement)\r\n   at Microsoft.Build.Evaluation.Evaluator`4.EvaluateImportElement(String directoryOfImportingFile, ProjectImportElement importElement)\r\n   at Microsoft.Build.Evaluation.Evaluator`4.PerformDepthFirstPass(ProjectRootElement currentProjectOrImport)\r\n   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate()\r\n   at Microsoft.Build.Evaluation.Evaluator`4.Evaluate(IEvaluatorData`4 data, ProjectRootElement root, ProjectLoadSettings loadSettings, Int32 maxNodeCount, PropertyDictionary`1 environmentProperties, ILoggingService loggingService, IItemFactory`2 itemFactory, IToolsetProvider toolsetProvider, ProjectRootElementCache projectRootElementCache, BuildEventContext buildEventContext, ProjectInstance projectInstanceIfAnyForDebuggerOnly)\r\n   at Microsoft.Build.Evaluation.Project.ReevaluateIfNecessary(ILoggingService loggingServiceForEvaluation)\r\n   at Microsoft.Build.Evaluation.Project.CreateProjectInstance(ILoggingService loggingServiceForEvaluation, ProjectInstanceSettings settings)\r\n   at Microsoft.FSharp.Compiler.SourceCodeServices.ProjectCrackerTool.Program.projectInstanceFromFullPath@124(FSharpProjectFileInfo this, ProjectCollection engine, String fsprojFullPath)\r\n   at Microsoft.FSharp.Compiler.SourceCodeServices.ProjectCrackerTool.Program.FSharpProjectFileInfo.CrackProjectUsingNewBuildAPI(String fsprojFile)\r\n   at Microsoft.FSharp.Compiler.SourceCodeServices.ProjectCrackerTool.Program.FSharpProjectFileInfo..ctor(String fsprojFileName, FSharpOption`1 properties, FSharpOption`1 enableLogging)\r\n   at Microsoft.FSharp.Compiler.SourceCodeServices.ProjectCrackerTool.Program.getOptions@358(Boolean enableLogging, FSharpList`1 properties, String file)\r\n   at Microsoft.FSharp.Compiler.SourceCodeServices.ProjectCrackerTool.Program.getOptions(String file, Boolean enableLogging, FSharpList`1 properties)\r\n   at Microsoft.FSharp.Compiler.SourceCodeServices.ProjectCrackerTool.Program.main(String[] argv)"
        }
    }
}

[Krzysztof-Cieslak]

Generally, it looks good to me. Just one thing - please make this PR to develop branch (templates folder) instead directly to templates branch. templates branch is meant to be "read-only" branch updated through FAKE build script by project maintainers.

[Vaub]

Done, see https://github.com/fsprojects/generator-fsharp/pull/23