Bug 26496: Add op field to Budget Planning

Bug 26496: Add op field to Budget Planning

Without this patch, it's impossible to save a budget plan.

With this patch, it is possible to save a budget plan.

Test:
1. Apply patch
2. Modify a budget (e.g. http://localhost:8081/cgi-bin/koha/admin/aqbudgetperiods.pl?op=add_form&budget_period_id=1)
3. Unlock the budget if necessary by unticking "Lock budget" and click "Save"
4. Go to a budget (e.g. http://localhost:8081/cgi-bin/koha/admin/aqbudgets.pl?budget_period_id=1)
5. Click "Planning" and "Plan by libraries"
6. Click "Auto-fill row" on the first line
7. Click "Save"
8. Note that results are saved and shown on the newly loaded page

To verify this patch is necessary, do the test plan without applying the patch.

Signed-off-by: Barbara Johnson <barbara.johnson@bedfordtx.gov>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>