wallet: increase lookahead configuration to 2 ** 32.

[nodech]

NOTE This requires migrations so needs to land in 5.x If there are any breaking changes to layout we want in DB, this is probably good time.

[coveralls]

Coverage: 68.289% (+0.09%) from 68.203% when pulling fa9cc462bf9a5cd67fe9de8c1eede78159bd3163 on nodech:account-lookahead into 309df94ad5b2874944a32de63b449ac0a542068d on handshake-org:master.

[pinheadmz]

Concept ACK, didn't test code yet but looks like the right approach with migration. Question: should we add an RPC to bump up lookahead on existing accounts? Looks like the only way to set a non-default lookahead with this branch is when you create something

[nodech]

yeah, I believe it only matters when creating account/wallet. Modifying existing accounts lookahead vs adding new account both require rescan to have a proper state, so I would say it will be preferred to just create new wallet/account or recreate account is better in general for that reason. It is easier to understand that adding new account needs rescan.

[pinheadmz]

I also rebased your branch on master and will f-push