IVGCVSW-3726 Doxygen touch-up

 * Doxygen comment touch-ups
 * Fixed markup in .dox files
 * Fixed stylesheet
 * Doxyfile changes
 * Added logo file
 * Added header file

Signed-off-by: Ryan OShea <Ryan.OShea2@arm.com>
Change-Id: I94c7f5a6923a0bbb5c6ed610f1f55d57e2bb8a49
diff --git a/docs/Doxyfile b/docs/Doxyfile
index 8f104cb..67a8eeb 100644
--- a/docs/Doxyfile
+++ b/docs/Doxyfile
@@ -74,7 +74,7 @@
 # pixels and the maximum width should not exceed 200 pixels. Doxygen will copy
 # the logo to the output directory.
 
-PROJECT_LOGO           =
+PROJECT_LOGO           = ./docs/Arm_NN_horizontal_blue.png
 
 # The OUTPUT_DIRECTORY tag is used to specify the (relative or absolute) path
 # into which the generated documentation will be written. If a relative path is
@@ -1189,7 +1189,7 @@
 # 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            = ./docs/header.xhtml
 
 # 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