org-odt.el: Support for styling of tables using table templates
* contrib/lisp/org-odt.el (org-odt-table-style)
(org-odt-table-style-spec): New variables.
(org-export-odt-table-styles): New user-customizable variable.
(org-odt-begin-table): Init `org-odt-table-style' from the
attributes.
(org-odt-get-table-cell-styles): New function.
(org-odt-end-table): Use the above function.
(org-odt-get-style-name-for-table-cell): Removed. Now folded
in to `org-odt-get-table-cell-styles'.
(org-odt-get-style-name-cookie-for-table-cell): Modified to
accommodate new user-defined styles.
Users now have the option of choosing Org's own way of styling or
using custom styling.