Merged Gianluca's html output branch.

Merged Gianluca's html output branch.

Changes to merge with my branch:

  * Added some reference to "be html" or "becommands/html.py" in his
    new bugs' summaries.  Bug titles should make clear to which aspect
    of our growing repository they refer.
  * Fixed unittests in becommands/html.py.
  * execute() kwarg "test"->!"manipulate_encodings
  * bugdir.simple_bug_dir() -> bugdir.SimpleBugDir()
  * bd.cleanup() at end of unittests