add visual studio 2013 fsharp project template

Microsoft Visual Studio Premium 2013
Version 12.0.21005.1 REL
Microsoft .NET Framework
Version 4.5.51641

Installed Version: Premium

Visual F# 2013   06191-004-0456024-02825
Microsoft Visual F# 2013
Merge pull request #277 from enricosada/vs2013_templates

add visual studio 2013 fsharp project template
Adjust project files to allow editing with Xamarin Studio
Enable portable-net45+sl5+win8 profile (Profile7)
Updates to Profile7 support
Fix https://github.com/fsharp/fsharp/issues/282
Fix https://github.com/fsharp/fsharp/issues/196
add Sample_VS2012_FSharp_Portable_Library_upgraded_2013
Merge branch 'master' of https://github.com/fsharp/fsharp
Fix https://github.com/fsharp/fsharp/issues/283: build 2.3.5.0 FSharp.Core PCL assembly