[SoM] tools/dora should search the code base for the result

[stephen-hawley]

Currently the output of dora is something like:
kCantHappenBase + 2
Instead it should really be something like
ClassInventory.cs:35: throw ErrorHelper.CreateError (InventoryError.kCantHappenBase + 2, $"Expected a top level definition to have a class name.");

which can probably be done with:
fgrep --include=\*.cs -rnw '..' -e 'kCantHappenBase + 2,'