Tweak looks of API documentation.

WIP:
 * Only a first subset of CSS has been applied
 * Look based on Humdinger's and other's work on user guide
 * Navigation is still ugly. I need to work around the limitations of Doxygen. Maybe by a patch though.
 * Needs a manual extra step: you need to copy the /trunk/docs/userguide/images/logo.png to the /trunk/generated/doxygen/html directory

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@29117 a95241bf-73f2-0310-859d-f6bbb57e9c96

docs/user/Doxyfile

@@ -683,7 +683,7 @@ HTML_FILE_EXTENSION    = .html
 # each generated HTML page. If it is left blank doxygen will generate a 
 # standard header.
 
-HTML_HEADER            = 
+HTML_HEADER            = header.html
 
 # The HTML_FOOTER tag can be used to specify a personal HTML footer for 
 # each generated HTML page. If it is left blank doxygen will generate a 
@@ -698,7 +698,7 @@ HTML_FOOTER            = footer.html
 # the style sheet file to the HTML output directory, so don't put your own 
 # stylesheet in the HTML output directory as well, or it will be erased!
 
-HTML_STYLESHEET        = 
+HTML_STYLESHEET        = book.css
 
 # If the HTML_ALIGN_MEMBERS tag is set to YES, the members of classes, 
 # files or namespaces will be aligned in HTML using tables. If set to