Better Universal Dependencies support

[David McClosky]

This would involve at least the following:

1. Add the -originalDependencies option for both backends.
2. Find a way to download the feature mapping and include it in the classpath. It's included in the giant models jar files, so we could include those, but it seems overkill to download these if we can avoid it.
3. Populate the features field with features from universal dependencies (requires 2.)
4. Map the POS tags to their Universal counterparts.