allow .tar, .zstd reference and equilibrium archives

NOTE: now requires eq_zip to be specified in config.nml if eq_url is being used to download and extract. This avoids ambiguous situations.

Allow .zstd and .tar along with .zip to be used. We've found reliability issues with corrupted .zip and given broad acceptance of .zstd and faster, more compression we are using .zstd for archives for reference data and equilibrium data.