Create OriginalFile Model

[avrohomgottlieb]

This Epic is meant to track all issues connected with the creation and integration of the OriginalFile model into the codebase. This model will allow us to cache information about the files in the s3 input bucket for the purpose of minimizing calls across the network, as well as determining the integrity of computed files for projects and datasets (as the contents of the s3 input bucket are regularly updated).