[IMP-dev] Cleanups to kernel and doxygen.conf

The patch has some more changes to the kernel documentation as well as cleaning up the doxygen.conf file to remove extraneous stuff. If you want to see doxygen information involving .cpp files (which are not documented in general), use the doxygen.conf in kernel/doc/internal (although you may want to wait until to check more tomorrow). I can't imagine why you would want to use those other docs though :-)