Previously we populated the reference body into all <ref> tags
with the same key. Now we store an internal attribute marking
which element originally had the data.
If that tag is deleted the body is moved to the first <ref> tag
with that name.
Change-Id: If9f12bfb699e6ce85bb8f7d2ea9e6df528610a3d
Created an IndexValueStore class which can store any object and return
an integer index to its hash map.
Linear data is now stored in ve.dm.LinearData instances. Two subclasses
for element and meta data contain methods specific to those data types
(ElementLinearData and MetaLinearData).
The static methods in ve.dm.Document that inspected data at a given
offset are now instance methods of ve.dm.ElementLinearData.
AnnotationSets (which are no longer OrderedHashSets) have been moved
to /dm and also have to be instantiated with a pointer the store.
Bug: 46320
Change-Id: I249a5d48726093d1cb3e36351893f4bff85f52e2
