Updated the broken GetStarted instructions.  In particular, the CDE package and the installation script for Ubuntu 12.04 were outdated and have been removed.  The old STP repository does not exist anymore, so we are now providing an archive instead.  The instructions for klee-uclibc have not been updated yet, although a new version is under way.
A proofreading pass over GetStarted.html
Updated doxygen link + minor change.