Fix EZP-23812: vertical align in table cells is not visible in the editor

JIRA: https://jira.ez.no/browse/EZP-23812

# Description

The vertical alignment of the table cells (and headers) is not reflected in Online Editor. Before this patch, the content of a cell is always in the middle (even if the default vertical align is top).

With this patch:

![oe_valign](https://cloud.githubusercontent.com/assets/305563/5485518/8d6e8a84-869c-11e4-9a7d-218a6deb6b72.png)


# Tests

manual tests