- exercise editor site test file upload, attach, detach, download file is working

src/ClientServer/Config/Constants.cs

...ollers/Core/CustomProjects/EditCustomProjectController.cs

...xerciseAfterSolution/DoExerciseAfterSolutionController.cs

...Server/Controllers/Core/Exercises/DoExerciseController.cs

...er/Controllers/Core/Exercises/ExerciseEditorController.cs

...tServer/Controllers/Core/Exercises/TestAssetController.cs

...ntrollers/Core/Exercises/TutorViewAssessmentController.cs

src/ClientServer/Controllers/Core/Init.cs

src/ClientServer/Controllers/Core/Login/AuthController.cs

src/ClientServer/Db/SyndromDBContext.cs

src/ClientServer/Helpers/Files.cs

...rations/20190601145551_ExerciseTestAssetFiles.Designer.cs

...erver/Migrations/20190601145551_ExerciseTestAssetFiles.cs

src/ClientServer/Migrations/SyndromDbContextModelSnapshot.cs

.../Exercises/ExerciseDescriptionWithFileAsAssetReference.cs

src/ClientServer/Models/Exercises/Tests/Test.cs

...er/Models/Exercises/Tests/TestWithFileAsAssetReference.cs

src/ClientServer/Models/Files/FileReferenceTestAsset.cs

src/ClientServer/Models/Files/FileReferenceUserFileAssets.cs

src/ClientServer/appsettings.json