Limits for item property lists is too small/too global

Reported on Slack:
I’m having difficulty setting separate shipping prices for all the postal codes in my city. OB has a limit of 30. Can this limit be removed or increased to 180 please.

The limit in the code:

	// MaxListItems - max items in a listing
	MaxListItems = 30

Is used to limit everything in a listing that is a list. coupons, shipping services, images, moderators, etc. Also limits some stuff in posts and profiles.

The chances of the correct limits for all of these being the same is very small. I suggestion a 2 step process:

1. Create separate limit const for each limit but make them all equal the current 30
2. Raise shipping services to 200 to alleviate current issue.
3. Consider each limit for reasonability and potential resource impact and set appropriately. Many may have the same limit but they should still be managed separately. E.g. maybe we want a max of 10 images, 100 coupons, 100 shipping services, and 25 moderators.