Doxygen support added

Includes a doxygen config file, a mainpage.dox placeholder,
and a css file for making the pioneer badge.png not so huge.

doxygen/mainpage.dox

@@ -0,0 +1,20 @@
+/**
+\mainpage Introduction
+
+[Pioneer](http://pioneerspacesim.net) is a space adventure game set in the
+milkyway galaxy at the turn of the 31st century. The game is open-ended, and
+you are free to explore the millions of star systems in the game. You can land
+on planets, slingshot past gas giants, and burn yourself to a crisp flying
+between binary star systems.
+
+This documents the C++ source code. There is also the Lua-API documentation
+available after a `make codedoc` or from
+[here](http://eatenbyagrue.org/f/pioneer/codedoc/).
+
+There is important documentation on the
+[wiki](http://pioneerwiki.com/wiki/Pioneer_Wiki) on coding conventions, design,
+development model, how to get started with contributing to the project and more.
+
+_Fly safe_
+
+*/

doxygen/projectlogo.css

@@ -0,0 +1,8 @@
+/* This extra style sheet is needed to make the pioneer badge be not so huge */
+#projectlogo img
+{
+    width: 103px;
+    height: 103px;
+    background-repeat: no-repeat;
+    background-position: 0% 50%;
+}