Improve Doxyfile

Improve Doxyfile

* Add main page.
* Organize into sections.
* Add threading sources.
* Include SpatialAreaStore, LevelDB/Redis, sound, FreeType, and cURL in output.
* Add logo.
* Fix project name hardcoding.
* Remove PAPER_TYPE (only used when GENERATE_LATEX is enabled).
* Have dot render graphs as SVG (smaller, and works even if dot's text drawing functionality is broken).
* Enable built-in STL support.
* Enable search bar.
* Switch from header-bar based navigation to treeview based navigation.
* Enable dynamic HTML (collapses graphs).
* Enable generation timestamp.