org-odt: Force columns of tables to have the same width

org-odt: Force columns of tables to have the same width

* contrib/lisp/org-odt.el (org-odt-end-table): Associate table
columns with `OrgTableColumn' style.
(org-odt-format-source-code-or-example): Delete trailing
whitespace.

* contrib/odt/styles/OrgOdtAutomaticStyles.xml: Modify
`OrgTable' style to use a relative width of 90%. Effective
table width is now increased so that tables are not
congested. There could be a reverse problem of they being too
big. This is OK. Introduced `OrgTableColumn' style and force
the columns to use the same width.

Fixes the following symptoms - congested table and uneven
columns - seen with the below report..

http://lists.gnu.org/archive/html/emacs-orgmode/2011-08/msg01053.html

Table cookies can specify default column width. These could be
used for finer control of column widths on per-table
basis. However this introduces the need to create automatic
column styles for each and every column that is explicitly
sized. The exporter has so far avoided creating of automatic
styles `on the go' and instead relied on a custom styles for
formatting. If column-widths are made user-controllable then
this has to change and the exporter could become a bit
inelegant. Is the overhead worth it?