[gnome-db] Mergeant forms status

[Vivien Malerba <malerba gnome-db org>]

Hi!

I've commited the latest work on the mergeant forms. It is now possible
to do INSERT, UPDATE and DELETE operations for the tables. You'll
notice, at the right or each data enty in any form a small vertical bar:
it is used to do some special actions on the corresponding entry (set to
NULL, set to default value) and shows the current status of the entry
(green for a NULL entry, blue for an entry set to the default value, red
if the entry must be modified before any commit and gray if none of the
previous status applies).

There are however still some work to be done:
* UI bugs
* error handling
* date/time displays are buggy
* default values are not handled when SQL queries are generated

Cheers,

Vivien