Improve trace processing experience

[J08nY]

During analysis, one usually starts of with a trace set (or more trace sets), then processes and combines the traces into one or more intermediary traces and finally produces some final trace for display/distinguishing/etc. During this, it is usually not necessary to keep all the intermediate traces and one is only interested in the result.

This should be made easier via some API. Not sure what the right pattern should be though.