Console - Properties that are 'multiple' can change type when adding/deleting values or don't allow adding values

To reproduce changing of type 1:

• Create a node 'test' under the root node
• Add a multiple property with type Long
• Leave value empty and click OK
  ! The type becomes String

To reproduce changing of type 2:

• Create a node 'test' under the root node
• Add a multiple property with type Long
• Set the value to 1000 and click OK
• Add or delete the value
  ! The type becomes String

To reproduce not allowing to add a value:

• Go to a document prototype node (hipposysedit:prototype)
• Add a multiple Long property with value 1000
• Try to add a value to the property
  ! The value is not added, and the following message shows in the log:
  ERROR [http-8080-5] [org.hippoecm.frontend.plugins.console.editor.PropertiesEditor$2.onClick():130] conversion failed: String to Long