initial reformatting of comments for Doxygen

sphere.cpp

@@ -1,6 +1,10 @@
 // Hyperbolic Rogue -- spherical spaces
 // Copyright (C) 2011-2018 Zeno Rogue, see 'hyper.cpp' for details
 
+/** \file sphere.cpp
+ *  \brief spherical spaces
+ */
+
 namespace hr {
 
 // --- spherical geometry ---