(bug 45043) Overhauled site input field of wbclient.linkItem.js

Overhauled the site input field of wbclient.linkItem.js to fix
bug 45043 and to match the behaviour of the repo input field.

Minor changes.

Change-Id: I2d24704f8f406d1c19d974c64044444e8ca17bb4
Merge "(bug 45043) Overhauled site input field of wbclient.linkItem.js"