Unable to add/remove row/columns in IE8

Clicking any of the add/remove buttons for rows/columns appears to be busted in IE8.
I missed to mention this in the commit description. We now have an object for startup functions. But since it is not complete, I didn't yet move it into its own file. Many of what is in `core.js` deserves to be there. In fact, `core.js` deserves to be much more modular. So perhaps, even, a nested `WYMeditor.startup` object.