1. Now either <arg> or ARG or [ARG] were used to denote an option
argument. Let's be consistent and use ARG everywhere. An alternative
could be be <arg>, but I'm strongly against [ARG] since square brackets
traditionally denote something that is optional.

2. If argument is a file name, use FILE, not NAME or SRC

3. For options that require argument, add argument. List includes:
	-t|--tree
	-D|--images-dir (twice)
	-f|--file
   Maybe I missed something else, hopefully not.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>