Add meta training module

[isaacmg]

In order to incorporate meta-data we need to add modules to train the meta-data encoders. This issue should do the these things.

• Add a file meta_trainer.py this file should include all things necessary to train an meta encoder module to generate meta embeddings. It should be able to be called from the command line as follow python meta_trainer.py -p meta_config.json
• Add sample auto encoder model to be trained
• Add unit to test JSON config files