tool: add "address" command to print D-Bus address

tool: add "address" command to print D-Bus address

This would be helpful to debug with dbus-monitor.  Instead of:

  $ . .config/ibus/bus/*
  $ dbus-monitor --address $IBUS_ADDRESS ...

one can do:

  $ dbus-monitor --address $(ibus address) ...

This patch also adds help message to each sub-command.

BUG=

Committed: 1f2a94e

[Peng, 2013-07-26 14:33:42]

https://codereview.appspot.com/11901044/diff/1/tools/main.vala
File tools/main.vala (right):

https://codereview.appspot.com/11901044/diff/1/tools/main.vala#newcode332
tools/main.vala:332: GLib.Intl.textdomain(Config.GETTEXT_PACKAGE);
Could you please explain why add this? Thanks.

[Daiki Ueno, 2013-07-27 00:07:51]

On 2013/07/26 14:33:42, Peng wrote:
> https://codereview.appspot.com/11901044/diff/1/tools/main.vala
> File tools/main.vala (right):
> 
> https://codereview.appspot.com/11901044/diff/1/tools/main.vala#newcode332
> tools/main.vala:332: GLib.Intl.textdomain(Config.GETTEXT_PACKAGE);
> Could you please explain why add this? Thanks.

This sets the default domain for gettext(), dgettext(null, ...), etc. 
bindtextdomain() doesn't set the default but select a catalog.  Currently,
gettext() happens to work without the default, as it looks at the selected
catalog, but setting the default would be safer.  Maybe good to do that as well
for the panel.

cf.
https://git.gnome.org/browse/gnome-contacts/tree/src/main.vala#n26
https://git.gnome.org/browse/gnome-clocks/tree/src/main.vala#n22

[Peng, 2013-07-27 02:43:34]

On 2013/07/27 00:07:51, Daiki Ueno wrote:
> On 2013/07/26 14:33:42, Peng wrote:
> > https://codereview.appspot.com/11901044/diff/1/tools/main.vala
> > File tools/main.vala (right):
> > 
> > https://codereview.appspot.com/11901044/diff/1/tools/main.vala#newcode332
> > tools/main.vala:332: GLib.Intl.textdomain(Config.GETTEXT_PACKAGE);
> > Could you please explain why add this? Thanks.
> 
> This sets the default domain for gettext(), dgettext(null, ...), etc. 
> bindtextdomain() doesn't set the default but select a catalog.  Currently,
> gettext() happens to work without the default, as it looks at the selected
> catalog, but setting the default would be safer.  Maybe good to do that as
well
> for the panel.
> 
> cf.
> https://git.gnome.org/browse/gnome-contacts/tree/src/main.vala#n26
> https://git.gnome.org/browse/gnome-clocks/tree/src/main.vala#n22

lgtm. thanks for explanation.

[Daiki Ueno, 2013-08-01 14:29:52]

Come to think of it, ibus_get_address() can be directly used instead of
ibus_bus_get_ibus_property(..., "Address").  I'll push the second patchset.