Support `max` property on custom properties

To enable custom property to have a specified maximum number of values, which in turn enables support for multi-value & single value properties

This should be possible for all places where custom properties are used in agreements and licenses

Property definition will now have a property named maxValues, that will drive the maximum number of values that can be entered. All the current property entries will be set to 1 where only 1 value exists (this should be all of them given the UI ensures 1 value in the array). Doing it this way means we can have a uniform UI for multiples and singles and limit the number of changes required.

maxValues will be configurable via the UI, but will not be able to be set to a more restrictive value.

• If not set (limitless), the value will not be configurable
• If set the number can not be set to a lower number but can be removed completely to make it limitless