Added voting period "adoption"

Caldera currently crashes with failure to parse "voting_period_kind" : "adoption".

This is for immediate deployment after we assure that it can work.

However it raises long term issues:

• there is no indication voting_period_kind at the current TezosAPI page
• Edo indicates that this field should be deprecated: https://tezos.gitlab.io/protocols/008_edo.html Should we parse it at all or remove and ignore it?