New uid and local/uid EntityReferenceSerializer<String>

Serialize a reference into a unique identifier string. This is faster compare to the human readable default string serializer and it provide unique reversible string without requiring complex escaping. Compare to default string serializer, it is aimed to be used only by computer and it will be kept stable over time. These string are comparable and could be used when an string identifier is required (ie: hashmap, caches, storage...). These strings are also a better source for hashing algorithms.

ie: The string created looks like 4:wiki5:space3:doc for the wiki:space.doc document and 4:wiki5:space3:doc20:wiki:xspace.class[0] for the wiki:space.doc^wiki:xspace.class[0] object.

The local/uid version is similar to the uid, but is made appropriate for a wiki independent storage. It never contains reference to the wiki itself.

ie: The string created looks like 5:space3:doc for the wiki:space.doc document and 5:space3:doc15:xspace.class[0] for the wiki:space.doc^wiki:xspace.class[0] object.