#299 Table caption alignment patch

[Istvan Toth]

The following patch adds the possibility to set the
table caption alignment.

The patch is against 2.3.1
Tested on Firefox 1.5 only.
No localization added.

I'd like to see this patch (perhaps cleaned up somewhat)
to go be applied, as it makes it possible to add bottom
captioned images to the document, which is not possible
with 2.3.1 (or at least I have not found a way)

[Istvan Toth]

Adds table caption alignment support to 2.3.1