Curve Metaregistry

TODO:

• Fix the pool removal logic to account for when a factory pool is removed from a registry (and therefore not from factory registry)
• Handle de-registering coins when a pool is removed
• Add categorization scheme and query for pools
• Add get_coin_indices
• Speed up test set up
• Fix / improve the is_active logic for registries
• Refactor get_A, get_gamma etc into get_params with buffer for potential future new pool params