Tweaks and fixes
- Unit quote broken by recent unit locking changes. Now fixed
- Tweaked wording on pack checkboxes in edit franchise to make it a little bit more intuitive
- Tender payment : readd nice UX feature lost from v4 : when you hit enter on tendered amount of 0, default tendered amount to the amount required
- Refined unit locking recently added, couple of scenarios where locking will not protect against simultaneous edits (when two sales are running at precisely the same time, highly unlikely but still possible). Now fixed.