Budget cumbersome for vesting schedules

[garious]

Problem

Using Budget to manage vesting schedules is a pain. We need to create 25 Budget contracts per vesting schedule (which there may be multiple per person) and then have the maintainer to send ApplyTimestamp to each of those contracts to get them to distribute tokens.

Proposed Solution

Add a new program Vest that manages a full vesting schedule. After creation, the creator should only interact with a specific contract in order to terminate it. Otherwise, it should simply publish dates to a single trusted account, an oracle account. To redeem tokens, the payee should send a RedeemTokens instruction to the vesting account, which would include the address of the oracle account.