Rethink overloads of find methods in internal object collections

The inadequacies of searching API can be mitigated by using Linq, but nevertheless it is desirable to have a better overloads for Find* methods. This can perhaps be better performance tuned than Linq. Little inefficiencies add up.

Also API can start using Symbol class than using a string for passing symbols. This will be a breaking change but it will make the API cleaner and more typesafe. Some API need to rethought like say FindBySymbol.