ExtJS style: fix improper layout.

@maethu @jone 
Also show dummy column in table body using the same width used in the header.
![bildschirmfoto 2013-05-30 um 07 50 36](https://f.cloud.github.com/assets/157533/583409/30db8b0e-c8ee-11e2-970b-c89016c0dd9c.png)