[Epic] Harvesting

[iafhurtado]

Create harvest function to ILending Provider Interface.

When a Lending Provider is not farming then it will return null.

Another function needs to be compoundingCollateral(LP, Asset)

Vault to handle swap and compound.

[pedrovalido]

Have the basic functions implemented before public launch

[pedrovalido]

protocols with rewards: compound dforce radiant spark

[pedrovalido]

First goal: lay down the structure, structs, interface functions, functions in contracts with general steps and comments

[pedrovalido]

Note to self: harvest logic will be done inside the vault (instead of having HarvestManager). No need to separate additional logic (like flashloan logic as in RebalancerManager and LiquidationManager), so no need to have HarvestManager.

[pedrovalido]

Note to self: HarvestManager will have to be implemented due to size in Vaults. It also makes sense to implement a HarvestManager to be able to implement specific strategies and extra complexities outside the vault (swap, distribute, etc).

[pedrovalido]

comment the function preview harvest from iharvestable and leave it as TODO function for later