Implement Parse "File Adapter" on Manta

[BobDickinson]

By default, Parse stores user files in MongoDB. A preferred implementation on Triton would be to use Manta for user file storage. There is a pluggable "File Adapater" solution that should support this:

https://github.com/ParsePlatform/parse-server/wiki/Configuring-File-Adapters

This should be enabled/configured via external config (docker-compose level) and is should be optional.