Adding in grid search

Cheat.exe
- Now able to eliminate words which cannot be formed on the grid
- Will now exit gracefully on unhandled exception

CheatTests
- Minor adjustment to the tests (since we now check for a 4x4 grid)
- Minor change to how cheat.exe output is recorded
- NOTE: for some reason TestContext.WriteLine is no longer viewable in
the testmethod (the output is turning up in the .trx file when I open it
in notepad, but under the resultsummary instead of a specific result).
Still investigating, but at worst I make it Console.WriteLine since that
is showing up correctly
- No new tests yet for GridSearch, will add that in next checkin