* Move more constants to const.py
* Import constants directly from const
* ATTR_ENTITY_ID is not defined in media_player
* MEDIA_PLAYER_PLAY_MEDIA_SCHEMA is still in __init__.py
* Correct imports in tts
* PLATFORM_SCHEMA, SCHEMA is still defined in __init__.py
* Pandora imports several services
* Some additional fixes for move of const in media_player
* Fix hound lengths
## Description:
More fixes flagged by pylint 2 that don't hurt to have before the actual pylint 2 upgrade (which I'll submit soon).
## Checklist:
- [ ] The code change is tested and works locally.
- [x] Local tests pass with `tox`. **Your PR cannot be merged unless tests pass**
