Bug 30599: Add an 'Archive selected' button

Bug 30599: Add an 'Archive selected' button

This patch simply adds a new button on the suggestions interface to allow
for archiving multiple suggestions.

To test:
1 - Apply patch
2 - Create some purchase suggestions
3 - Select several suggestions
4 - Click 'Archive selected'
5 - Suggestions are archived
6 - You can view archived suggestions by selecting 'Suggestion information'->'Include archived'

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Felicity Brown <felicity.brown@montgomerycountymd.gov>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>