some features that will make it slightly less fragile.
The code that registers a serializer for an ID has
been centralized.
A method was added to hand out new IDs and it now
skips IDs that are already in use. This will allow
certain serializers to be fixed against specific IDs
to maintain backwards and forwards compatability even
as the automatically registered list of serializers
changes.
git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@9455 75d07b2b-3a1a-0410-a2c5-0572b91ccdca
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