BIP 19: Reduce Initial DIGG Supply to 4,000

TLDR; Reduce initial DIGG supply from 6,250 to 4,000.

Rationale: lowering initial marketcap may lead to positive rebases which can have positive psychological effects on the community and ultimately, potentially greater positive impacts for the community.

See discussions here: https://forum.badger.finance/t/bip-19-reduce-initial-digg-supply-to-4-000/1504