Add back custom css for doxygen

docs/doxygen/Doxyfile

@@ -1316,47 +1316,29 @@ HTML_FILE_EXTENSION    = .html
 # of the possible markers and block names see the documentation.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_HEADER            = 
+
+HTML_HEADER            = ../_doxygen/header.html
 
 # The HTML_FOOTER tag can be used to specify a user-defined HTML footer for each
 # generated HTML page. If the tag is left blank doxygen will generate a standard
-# footer. See HTML_HEADER for more information on how to generate a default
-# footer and what special commands can be used inside the footer. See also
-# section "Doxygen usage" for information on how to generate the default footer
 # that doxygen normally uses.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_FOOTER            = 
+HTML_FOOTER            = ../_doxygen/footer.html
 
 # The HTML_STYLESHEET tag can be used to specify a user-defined cascading style
 # sheet that is used by each HTML page. It can be used to fine-tune the look of
-# the HTML output. If left blank doxygen will generate a default style sheet.
-# See also section "Doxygen usage" for information on how to generate the style
-# sheet that doxygen normally uses.
-# Note: It is recommended to use HTML_EXTRA_STYLESHEET instead of this tag, as
-# it is more robust and this tag (HTML_STYLESHEET) will in the future become
 # obsolete.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_STYLESHEET        = 
+HTML_STYLESHEET        = ../_doxygen/stylesheet.css
 
 # The HTML_EXTRA_STYLESHEET tag can be used to specify additional user-defined
 # cascading style sheets that are included after the standard style sheets
-# created by doxygen. Using this option one can overrule certain style aspects.
-# This is preferred over using HTML_STYLESHEET since it does not replace the
-# standard style sheet and is therefore more robust against future updates.
-# Doxygen will copy the style sheet files to the output directory.
-# Note: The order of the extra style sheet files is of importance (e.g. the last
-# style sheet in the list overrules the setting of the previous ones in the
-# list).
-# Note: Since the styling of scrollbars can currently not be overruled in
-# Webkit/Chromium, the styling will be left out of the default doxygen.css if
-# one or more extra stylesheets have been specified. So if scrollbar
-# customization is desired it has to be added explicitly. For an example see the
 # documentation.
 # This tag requires that the tag GENERATE_HTML is set to YES.
 
-HTML_EXTRA_STYLESHEET  = 
+HTML_EXTRA_STYLESHEET  = ../_doxygen/extra_stylesheet.css
 
 # The HTML_EXTRA_FILES tag can be used to specify one or more extra images or
 # other source files which should be copied to the HTML output directory. Note