Issue #1287686 by rjay: Prevented error message from appearing when a LayoutStudio theme/sub-theme has not been configured yet. Added a helpful warning message to the administrator to select a layout and configure the theme.
make wrapper for preface, content & postscript zones div in html5
doing so because, as quote by html5 doctor: "With very few exceptions, section should not be used if there is no natural heading for it."
Signed-off-by: rhache <firstname.lastname@example.org>