(Joint work with Vijay Peddinti), add recipe that supports non-contiguous splicing in the middle of the network.  This involved some refactoring of the core nnet2 code, to make the update efficient.  Need to add results and more example scripts... but it's about 1% abs better than previous online-nnet2 recipe.

git-svn-id: https://svn.code.sf.net/p/kaldi/code/trunk@4581 5e6a8d80-dfce-4ca6-a32a-6e07a63d50c8
trunk: implemented Read/Write for OnlineIvectorExtractorAdaptationState and some classes that it uses

git-svn-id: https://svn.code.sf.net/p/kaldi/code/trunk@4582 5e6a8d80-dfce-4ca6-a32a-6e07a63d50c8