Auto per-address consolidation (brainstorm)

[markblundeberg]

• Can't just naively consolidate everything we see because that would be a privacy risk.
• With new fusion protocol allowing more components, this will be less of an issue since >3 on one address is not so bad.
• By consolidating back to the same addr, the coin chooser still knows which txids are correlated.

Possible idea:

1. Every candidate addr has a certain chance per unit time of being consolidated.

   This can be implemented sanely by having fusion calculate the number N of consolidation candidates, then multiplying this by the base rate gamma. N*gamma is the rate of any address being consolidated. Fusion generates an exponential random timestamp according to this rate, and saves it in the wallet file. When the timestamp is reached, then a random consolidation candidate address is chosen and consolidated.

2. Not sure what the best choice for the base time constant is. 1 day, perhaps?