Fixed incorrect size hints for TableView

This ensures that double click to adjust content size on
headers doesn't end up eliding text. We also added
significantly more space by default.

Change-Id: I05a05649a41ef4b70ee839195a87c684786760b1
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@digia.com>