Add zeropad class to td, th elements

Part of a fix for https://bugzilla.novell.com/show_bug.cgi?id=859074 in https://github.com/crowbar/barclamp-provisioner/pull/315
Agreed. This is due to the fact that bootstrap uses a more specific CSS selectors for th/td: ```.table > tfoot > tr > td``` is more specific than ```table td.zeropad```. What would you suggest using here?