Import formatted ratings

[epugh]

Now you can export and import ratings in both csv and RRE formats!

Description

Refactors the Import Ratings screen to deal with two types of files. Enhances the API to take a ?file_format=rre' parameter to change from the default hash` of ratings format.

Motivation and Context

Support migrating ratings between Quepid and RRE depending on you type of task.

Part of fixing #133

How Has This Been Tested?

unit tests and manually.

Screenshots or GIFs (if appropriate):

Types of changes

• [] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• [] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• [] I have updated the documentation accordingly.
• [] I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.