change --foo_bar options to --foo-bar

rename options. (s/_/-/)
according to Isaku Yamahata, this makes us look similar to openstack.

caveat: no backward compat is provided.  you need to update both of
config files and cli options.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
update an example after option name changes

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
mechanical documentation update after option name changes

s/_/-/ in option names.

note: some parts of them (eg. eventdumper, nova, ...) looks outdated
but i didn't try to update them at least in this commit.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>