Check that config.py is setting the correct defaults for AlignmentEnhanced models.

[davidbaines]

Using silnlp.nmt.config to create AlignmentEnhanced models doesn't give the expected defaults.

When an SILTransformerBaseAlignmentEnhanced model is specified explicitly or used by the parent model then:
word_dropout should be set to 0
The coverage_penatly should be set to 0.1

We probably want the terms: dictionary: setting set to true.