Expose _id in ExtendedProperties subValues

* ExtendedValues' "name" and "value" columns are exposed in Entry
  entity subvalues, but it is clumsy to change a value, as the _id
  of the ExtendedValues row isn't also exposed.  (We otherwise have to
  perform a potentially slow query)
* This CL adds the _id column to the columns exposed

Bug: 2638762
Change-Id: Iaffeffed620af78439f5f73aa5f3257b0f8a0fd0