Re-apply "Added EntityId and EntityIdParser in JS"

The new data value is not yet in use, this will be done in a follow up which will also include all
necessary fixes for the UI.

patch set 4: rebase
patch set 6: don't use new data value type in production yet, do this as a follow-up

Change-Id: I0ffafe2b040f40715dfa03c529ece81b1e2d9d0b
Merge "Re-apply "Added EntityId and EntityIdParser in JS""