Modifications in Thematique.php, AddThematiqueType.php, ThematiqueHandler.php to handle the upload of a (image) file associated to a theme

	The following documentation has been followed: http://symfony.com/doc/2.3/cookbook/doctrine/file_uploads.html
Modification of the directory path to the uploaded files associated to a theme

	The attribute "path" of the theme entity has been modified to "private"

	TODO:	-When a theme is suppressed, the associated file is not. See: http://symfony.com/doc/2.3/cookbook/doctrine/file_uploads.html "Using Lifecycle Callbacks"
		-Modify the upload() method in Thematique.php to include the other processes in ThematiqueHandler before persisting
		-Do not use the same filename as the one uploaded by the user: http://symfony.com/doc/2.3/reference/forms/types/file.html
		-See the upload of a theme
Upload of the README
Modification of the filename from the client before uploading
Upload of an image when creating a new theme: added constraints on the format (PNG), dimensions (128*128) and size (<1024k)

	Comment: the translation of the error messages is automatically managed
Upload of the README
Display of the image associated to each theme in the tree root page
Display a default image for a theme when the user did not upload one