This PR moves chain config related code (config file processing, fork
logic, network defaults) from `beacon/types` and `beacon/blsync` into
`beacon/params` while the command line flag logic of the chain config is
moved into `cmd/utils`, thereby removing the cli dependencies from
package `beacon` and its sub-packages.
This change implements CommitteeChain which is a key component of the beacon light client. It is a passive data structure that can validate, hold and update a chain of beacon light sync committees and updates, starting from a checkpoint that proves the starting committee through a beacon block hash, header and corresponding state. Once synced to the current sync period, CommitteeChain can also validate signed beacon headers.
Felföldi Zsolt