Print stack trace on error signal.

Let any code that links to a debug version of libTeslaCommon print a stack trace on error (e.g. assertion failures).
Print instance name as part of State string.
Remove duplicate equivalence testing.

In fact, both versions of "is this transition equivalent to that one" were doing effectively the same thing.
Only look for the sub-string we care about.

With a real implementation of "put all equivalent TESLA transitions into a single struct tesla_transitions", we will need less brittle checking strings as in this change.
Move InstanceName() to Names.{h,cpp}.

InstanceName() converts reference vectors into strings like "(o,op,X)". We might like to use this in places other than the State class, such as transition debug code.