Revert "Merge branch 'refs/heads/remove_is_valid' into dev"

This reverts commit 6567675cbbb60f0408d450da77a00613414efc6e, reversing
changes made to 966adf7b90fec5415544be24dcf594f419b5c298.
Remove unique index on device_tokens
Add invalid token factory
Test for inheriting an invalid device token
Remove uniqueness test on device_token
Update create in Notifiable::DeviceTokensController

Only allow inheritance of valid tokens
Merge branch 'refs/heads/token_unique_when_valid' into dev
bump version