Update the models to use the latest `0.x`.

Fixes https://github.com/tensorflow/tfjs/issues/1282
Fixes https://github.com/tensorflow/tfjs/issues/1283

- Update each model to depend on tfjs `0.15.3`
- Remove all deprecated API (fromPixels, tensor.get(), loadModel, loadFrozenModel, data.forEachAsync)
- Remove private API imports such as from 'tfjs_core/dist/....'
- Migrate all models hosted on GCP to use the new model.json format
  - `ssd_mobilenet_v1`, `ssd_mobilenet_v2/`, `ssdlite_mobilenet_v2/`, `mobilenet_v1_1.0_224`, `mobilenet_v2_1.0_224`, `posenet_mobilenet_{025,050,075,100}_partmap`, `universal_sentence_encoder`, `toxicity`


- Align the lint and yarn commands across the models
- Tested that each model's demo is working by yalc linking the model's npm package `@master`.

INTERNAL