Implement Helper Functions

[ec2]

• hash
• hash_tree_root
• is_active_validator
• get_active_validator_indices
• shuffle
• split
• get_committee_count_per_slot
• get_shuffling
• get_previous_epoch_committee_count_per_slot
• get_current_epoch_committee_count_per_slot
• get_crosslink_committees_at_slot
• get_block_root
• get_randao_mix
• get_beacon_proposer_index
• merkle_root
• get_attestation_participants
• bytes1, bytes2, ...
• get_effective_balance
• get_fork_version
• get_domain
• verify_slashable_vote_data
• is_double_vote
• is_surround_vote
• integer_squareroot
• bls_verify
• bls_verify_multiple
• bls_aggregate_pubkeys

[decanus]

Shuffle should be implemented in a separate file, with a protocol that defines shuffle() function, so we can easily switch out if it is determined to change as noted in the spec.