multiselect separators are not defined for all list property types

Separators (the "separators" meta property) have two roles:

• one is to separate multiple values when storing a multipleSelect property in one field (multipleSelect = true, relationalStorage = false), either in the database or in a xml export
• and the other one is to separate values in a form field when the display type is plain input

For some reason, this property is only defined for StaticList properties, but it is used for all list properties. This causes XWIKI-1722, for example, and causes most list properties not to work as expected when using multipleSelect = true and displayType = input.

The fix would be to define separators in all ListProperties (just in the parent ListMetaClass and ListClass will suffice).