Add a first manual hookpoint

[deep-ink-ventures]

We are creating a manual hookpoint here that is a hardcoded contract call. We will abstract this in the subsequent tickets, once we have this worked out.

After the token balance is calculated here, do the following:

• check if the DAO owner address has a register_specific_ink_callback for the id ON_VOTING_CALC, if not check if the DAO owner address has a register_global_ink_callback on that address, if not do nothing
• if there is a contract, call it using https://crates.parity.io/pallet_contracts/pallet/struct.Pallet.html#method.bare_call, just use reasonable max limits that work for gas limits etc.; encode the params as defined in our trait and expect a return value as expected in our trait
• if there is any kind of error or unexpected return, emit an event and otherwise ignore and continue with the original value
• if no error is, continue with the returned value.

Note that use-ink/ink#1674 is discussing taking this one step further: Instead of us manually encoding and decoding between values, there is a way to automate this. We may want to take this ticket and implement it.