Adding the new machine and component documentation.
Adding tail.html (for automated documentation creation).
Adding head.html (for automated documentation creation).
Ooops. Forgot to add CommandInterpreter.cc
Ooops. Forgot to add exec_elf.h.
Ooops. Forgot to add mips_cpuregs.h.
Ooops. Forgot to add CommandInterpreter.h.
Merging in _everything_ from the old C++ branch.
Merging in the Command class from the old C++ branch.
Merging in the Checksum class from the old C++ branch.
