Remove (unnecessary) application launcher and add <setup> meta-data

[mahiuchun]

ibus-hangul seems to be the only engine that uses its own application launcher.
Though Unity from Ubuntu blocks the menu mode of IBus.
"Preferences" button in ibus-setup can be an alternative.
I've tested my commits on Ubuntu 12.04

Reference:
http://code.google.com/p/ibus/issues/detail?id=1495

[mahiuchun]

Do you really want to remove the application launcher entirely? (50e4967 and 8eee6ea)
Alternatively, you can just hide it.
3d88a6c seems unless for Fedora/IBus 1.4.99 environment. It is necessary for Ubuntu 12.04 environment though.

[choehwanjin]

Yes, let's remove it.
I prefer just 1 commit for this change.
ibus-setup should be able to launch ibus-setup-hangul without the commit 3d88a6c.
So, could you please make a commit for this change from the rest two commits 50e4967 8eee6ea.