Staking can choose a reward type

[shannonwells]

As a Frequency account holder, I want to be able to choose whether my stake targets a provider only for capacity (Maximum Capacity) or to split between token reward and Provider Capacity (Provider Boost).

Acceptance Criteria (In):

• the stake extrinsic accepts a staking_type parameter, which is one of two enums, MaximumCapacity,ProviderBoost (naming is not set in stone).
• the resulting StakingAccountDetails reflects this choice
• the Capacity generated for the Provider reflects this choice (can be stubbed out with some constant value if needed)

Out:

• any other effects such as earning actual token rewards
• storage migration for StakingAccountDetails

[shannonwells]

Finished with bba4a02

[shannonwells]

Finished with bba4a02