Add Tag Categories

When using many Tags to organize your Decks or importing Shared decks with a lot of tags, the List gets confusing. My suggestion is to maybe have the ability to categorize Tags into folders or some sort of deck specific sorting

You can already organize your tags in trees, like you can do for decks. E.g. Math::Differential_Equations.
Also, a new tag editor will be available in 2.1.50