Sweep through code, looking for consistency issues

The git-clang-format + tidy probably do a reasonable job of making the code look consistent, however there are places (in fit performer for sure), where I've not been completely consistent.  For instance, class members having trailing vs leading underscores, stuff like that.  Lets clean that up.  

While there, look for things we'd like to avoid (like, don't do the implicit conversion of a std::shared_ptr to boolean, but compare to nullptr instead).  Stuff like that.  Examine pubic interfaces, for things that could be private, etc...