CMS-2177 Make a persisting version of ItemDao
Added precondition for source when creating Path Builder based on another Path
CMS-2216 Design Item API
Added constant for the root ItemPath
CMS-2216 Design Item API
Added property icon to Item, so icons can be persisted (since we do not have support for binaries in data.Value)
Added parent ItemPath to Item and changed Item.path to resolved from parent path and name upon creation time.
Added ItemEditor.getReadAt to be able give user a notification if the Item being updated have been updated somebody else after it was read by the user
CMS-2177 Make a persisting version of ItemDao
CMS-2215 Let a Mixin be persisted as an Item
CMS-2201 Create Relationship for Item