Doc: Improve selection of offline template type

Qt 5.6 now includes a version of the offline documentation template
with simplified CSS suited for rendering HTML with a QTextBrowser
backend.

Select the template in qt-html-templates-offline.qdocconf, instead
of the higher-level qt-module-defaults-offline.qdocconf. This is
better because many projects external to qt5 (including Qt Creator)
do not use qt-module-* includes. This way, we can control the
template selection for all projects from a config file.

Change-Id: I766af422d829f3c9519c5a45093473175363d600
Reviewed-by: Martin Smith <martin.smith@digia.com>

doc/global/qt-html-templates-offline-simple.qdocconf

-#include standard set of HTML header and footer.
-include(html-config.qdocconf)
-include(html-header-offline.qdocconf)
-include(html-footer.qdocconf)
-
-# Uncomment if navigation bar is not wanted
-#HTML.nonavigationbar      = "true"
-
 # Specify a custom CSS file used by this template
 HTML.stylesheets  += template/style/offline-simple.css
 qhp.extraFiles    += style/offline-simple.css
 
-# override the header styles
+# Override the header styles
 HTML.headerstyles  = \
     "  <link rel=\"stylesheet\" type=\"text/css\" href=\"style/offline-simple.css\" />\n" \
     "  <script type=\"text/javascript\">\n" \

doc/global/qt-html-templates-offline.qdocconf

@@ -26,3 +26,8 @@ qhp.extraFiles +=   style/offline.css \
                     images/bullet_dn.png \
                     images/bullet_sq.png \
                     images/bgrContent.png
+
+# By default, include override definitions for a simplified template/CSS,
+# suited for rendering HTML with QTextBrowser. Comment out this line to
+# select the standard CSS.
+include(qt-html-templates-offline-simple.qdocconf)

doc/global/qt-module-defaults-offline.qdocconf

@@ -8,10 +8,7 @@ include(compat.qdocconf)
 include(manifest-meta.qdocconf)
 include(fileextensions.qdocconf)
 
-# By default, select the 'simple' offline template, suited for rendering
-# HTML with QTextBrowser.
-include(qt-html-templates-offline-simple.qdocconf)
-#include(qt-html-templates-offline.qdocconf)
+include(qt-html-templates-offline.qdocconf)
 
 #extra configuration data such as file extensions
 include(config.qdocconf)