Per-round matching fund smoothing

[spengrah]

Smooth out the matching fund amounts per round.

This is important for (at least) the following reasons:

1. There may be an attack vector relating to intentionally spiking the matching funds of a given round
2. If recipients have reason to expect a future round could have significantly higher matching funds, they may delay participation to conserve their social & marketing capital in case that happens. This would have the effect of diluting the quality of recipients in current rounds.
3. The existence of funding for future rounds will imbue users/participants/stakeholders with a level of incremental confidence in the system as a whole.

Potential implementations:

• Matching funds are contributed to an "endowment" pool. Each round draws its matching funds from X% (e.g. half) of the existing funds in the endowment pool.
• We set (gradually increasing?) per-round matching fund caps. All matching funds contributed beyond the cap of the upcoming round are automatically allocated to the following round, and so on.

[auryn-macmillan]

Closing this for now.