std::set<T> instead of std::vector<T>?

[Yurlungur]

There are a number of places throughout Parthenon where we either use std::vector<std::string> or std::vector<Metadata>. Perhaps we should move to std::set, which is unique and ordered, and has a count method to check for existence. This would allow for validation logic like "is a particular variable string that I care about in this list of variable names?" for example.

What do people think?

[pgrete]

I think this would make sense.
It also add a kind of failsafe to not have duplicate entries by definition.