Bug 12147: Convert action links on invoices pages to a menu

Prior to this patch, the column for displaying the action links
was too narrow, leading to an ugly display.  This patch groups
"action" links into a menu as was done with Bug 11763.

This patch also converts the date column sorting configuration to use
header class instead of an index.

This patch also corrects a couple of HTML markup errors: An
improperly-closed <input> and an improperly closed <option>.

To test, view the invoices page and confirm that the "Actions" menu
button works corectly. Test the functionality of each menu options:
Details, Close, Reopen, and Delete. Confirm that sorting by billing date
still works correctly.

Much nicer user interface. Followed test plan. Works as expected.
Signed-off-by: Marc Véron <veron@veron.ch>

Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>