Cannot load any MSBuild project in Visual Studio 2013 - visual-studio-2013

Question

I've just started learning MSBuild and tried to load the below simple test project to Visual Studio 2013 (Update 5), but I'm getting the error 'The project system has encountered an error' - 'The given key was not present in the dictionary.'
Note I can successfully build the project with MSBuild from command line, just want to see it in VS project tree as part of a solution among the other csproj/vcxproj/etc. projects.
I've tried several ways, changing bits and pieces in msbuildproj file, etc. - no success, always getting the same error. Any idea what I'm doing wrong? Are MSBuild projects not supposed to be added to VS solution?
<!-- mytest.msbuildproj -->
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" >
<Target Name="Build">
<Message Text="Building my target" />
</Target>
</Project>
The project system has encountered an error
VsProjectFault_8c79b7c1-086a-47e9-be8c-46300a431de3.failure.txt:
=====================
01/03/2016 17:10:25
Recoverable
System.AggregateException: One or more errors occurred. ---> System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at Microsoft.Collections.Immutable.ImmutableDictionary2.get_Item(TKey key)
at Microsoft.VisualStudio.ProjectSystem.Designers.PhysicalProjectTreeProvider.GetProjectRootProperties(ConfiguredProjectExports configuredProjectExports)
at Microsoft.VisualStudio.ProjectSystem.Designers.PhysicalProjectTreeProvider.GenerateOriginalTree(ConfiguredProjectExports configuredProjectExports, CancellationToken cancellationToken)
at Microsoft.VisualStudio.ProjectSystem.Designers.PhysicalProjectTreeProvider.<GenerateOriginalTreeAsync>d__35.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at Microsoft.VisualStudio.ProjectSystem.Utilities.Designers.ProjectTreeProviderBase.<>c__DisplayClass9.<<Initialize>b__5>d__b.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Microsoft.VisualStudio.ProjectSystem.Utilities.CommonProjectSystemTools.Rethrow(Exception ex)
at Microsoft.VisualStudio.ProjectSystem.ProjectErrorReporting.<>c__DisplayClass5.<SubmitErrorReport>b__3()
at Microsoft.VisualStudio.ProjectSystem.ExceptionFilter.<>c__DisplayClass2.<Guard>b__0()
at GuardMethodClass.GuardMethod(Func1 , Func2 , Func2 )
--- End of inner exception stack trace ---
---> (Inner Exception #0) System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at Microsoft.Collections.Immutable.ImmutableDictionary2.get_Item(TKey key)
at Microsoft.VisualStudio.ProjectSystem.Designers.PhysicalProjectTreeProvider.GetProjectRootProperties(ConfiguredProjectExports configuredProjectExports)
at Microsoft.VisualStudio.ProjectSystem.Designers.PhysicalProjectTreeProvider.GenerateOriginalTree(ConfiguredProjectExports configuredProjectExports, CancellationToken cancellationToken)
at Microsoft.VisualStudio.ProjectSystem.Designers.PhysicalProjectTreeProvider.<GenerateOriginalTreeAsync>d__35.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task)
at Microsoft.VisualStudio.ProjectSystem.Utilities.Designers.ProjectTreeProviderBase.<>c__DisplayClass9.<<Initialize>b__5>d__b.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Microsoft.VisualStudio.ProjectSystem.Utilities.CommonProjectSystemTools.Rethrow(Exception ex)
at Microsoft.VisualStudio.ProjectSystem.ProjectErrorReporting.<>c__DisplayClass5.<SubmitErrorReport>b__3()
at Microsoft.VisualStudio.ProjectSystem.ExceptionFilter.<>c__DisplayClass2.<Guard>b__0()
at GuardMethodClass.GuardMethod(Func1 , Func2 , Func2 )<---
===================

Answer 1

Not all msbuild files are created equal. Sure you can craft one from scratch, and run it on the command line. But that doesn't mean visual studio will like that file.
Visual studio needs a msbuild file with a certain schema, and the above file doesn't fit the bill.