translation: Add complete Chinese(zh) translation

Fixes #514

Squashed commit of the following:

commit fc4670eb9ba9f7cf8ac3180c4036a61535130a94
Author: Feather Andelf <andelf@gmail.com>
Date:   Sat Feb 2 21:05:09 2013 +0800

    l10n/translation: fix missing underscore in admin_overview.tpl

commit 2a0c178f1558f573ae8e081365c52ffabc971bc8
Author: Feather Andelf <andelf@gmail.com>
Date:   Fri Feb 1 14:58:54 2013 +0800

    l10n/translation: fix missing underscore translate tag in media upload dialog

commit 5d94f9e4402323c9199b09400be6e4b8ca778a5f
Author: Feather Andelf <andelf@gmail.com>
Date:   Fri Feb 1 00:22:37 2013 +0800

    l10n/translation: fix mixing translation underscore in .tpl & .erl

commit 44ab45d2463503e7c70df817d5be08d9ca4441bf
Author: Feather Andelf <andelf@gmail.com>
Date:   Thu Jan 31 21:56:46 2013 +0800

    translation: Added complete chinese translation(zh)

commit c6d8630c12758b05fef4512c1214ab0f74e584b7
Author: Feather Andelf <andelf@gmail.com>
Date:   Thu Jan 31 01:05:10 2013 +0800

    translation: add more chinese translation, fix typo

commit 93a49d68ce3e8bb07b623193e1b01b4af4097746
Author: Feather Andelf <andelf@gmail.com>
Date:   Mon Jan 14 15:07:33 2013 +0800

    zh translation: update some translation, fix typo

commit 1163281344daeefaf766cda07c5bacc3ffa7adbc
Author: Feather Andelf <andelf@gmail.com>
Date:   Sun Jan 13 14:24:53 2013 +0800

    translations: Chinese(zh) translations by Shuyu Wang aka andelf

commit b6c4ce8c47cd679231f3697909e160bdc8123ef9
Author: Feather Andelf <andelf@gmail.com>
Date:   Sat Jan 12 00:55:35 2013 +0800

    translations: Chinese(zh) translations by Shuyu Wang aka andelf