Added libbe.TESTING (defaults to False).

Added libbe.TESTING (defaults to False).

This flag allows us to skip unittest and testsuite declaration if we
woln't need them.  It speeds up simple be calls a suprising amount.
With Testing=True (the old behavior):
  wking@thor:be.wtk$ time ./be > /dev/null

  real    0m0.393s
  user    0m0.340s
  sys     0m0.048s
With TESTING=False (the new behavior):
  be.wtk$ time ./be > /dev/null

  real    0m0.216s
  user    0m0.152s
  sys     0m0.064s

This adjustment was inspired by Jakub Wilk's Debian bug:
  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=559295