Add desktop menu for ibus-setup-hangul

Add desktop menu for ibus-setup-hangul

The install location of ibus-setup-hangul has changed to ${bindir}.
And the desktop file for ibus-setup-hangul is also installed in
${datadir}/applications.
Now it's easer to launch ibus-setup-hangul without palette or systray
icon. In ubuntu, unity does not allow the systray application to handle
mouse left button press event. So ibus does not show ibus engine
specific context menu. This makes users hard to change ibus-hangul's
configration.