Make SolvesController.totalMeanAverage respect whether or not a solve is completed
Add SolveView to restore old functionality, and a current_solve template to differentiate

current_solve template removes the need to track an "isResolved"
property and complicated architecture.
Add comment to explain the purpose of the timeDifference helper
Cleanup
Restore old trash functionality to Solve records

The trashed status still doesn't affect persistence, but prevents
trashed records from affecting computed session stats.