* FileSystemController.cs: Fixes the route to user's Files by an
Admin.
* FileSystemManager.cs: * Fixes the dir separator usage
* Adds a method to validate a directory or file name
* YavscModel.csproj:
* Commande.cs: FileInfoCollection is now removed
* FileInfoCollection.cs:
* DirNotFoundException.cs: Removes useless code
* CalendarController.cs: removes useless spaces
* FrontOfficeApiController.cs: Makes the tex to pdf exceptions
available to the user interface, as part of the application process.
Cleans the using clauses.
* TexToPdfFormatter.cs: sets the filename as response header.
* Web.csproj: a new FormatterException, thrown when exit code of
texi2pdf is not null
