VMM: Unified parameter names and option names.
handler: Handler.user_delete() renamed parameter:
delete_home -> del_dir
The same as in Handler.domain_delete().
cli/subcommands: renamed userdelete's option
--delete-home -> --delete-directory
So people have to memorize only one option name. It also matches the
setting names of vmm.cfg.
=============
Upgrading vmm
=============
Upgrade instructions for different versions of vmm.
.. toctree::
:maxdepth: 1
upgrade/0.5-0.6
upgrade/0.4.x-0.5