Do not enable object resizing in gecko

This table feature can make a mess of the table, in an unrecoverable way. Here is what I managed to do:
![screenshot from 2014-12-17 22 15 15](https://cloud.githubusercontent.com/assets/635591/5478127/4ca172ee-863a-11e4-80a1-7e02e4980239.png)

So I think this should be removed, with an appropriate message in the changelog.