feat: Time lock integration

[aszepieniec]

• Use and enforce time-lock logic for UTXOs that come with time-locks. Specifically:
  • Before release, the transaction is invalid.
  • After release the transaction is valid (or at least, not invalidated by the time-lock).
  • No effect on UTXOs that are not time-locked.
• Time-lock premine allocations for six months following launch.
• Convenience methods for computing available and time-locked balances.
• User-facing methods for reporting on available and time-locked balances and UTXOs.
• Drop support for partially proven transactions. This is a headache to work with. Better to add back later.
• Revise consensus logic abstractions. I'm still not happy with these though but this will be addressed in a later PR.

Closes #111.