Update to use revised Submission message

[BK-Teisrud]

QuickFeed issue quickfeed/quickfeed#433 present a new method for processing scores and buildInfo objects on the server. Here scores and buildInfo will be sent from server as proto objects and not JSON strings. This issue will be closed by the PR quickfeed/quickfeed#384.

SwiftUI frontend needs to be updated with the new form of score and buildInfo.

This issue will eliminate the use of ProtoExstensions.swift.