What happens to income details when the group mincome changes?

[mmbotelho]

Problem

When the group's mincome changes, the information entered by members on their income details modal can become outdated.

Solution

Mincome changes, the user was receiving. We should automatically calculate:

• If they now need more money, and update the amount they need;
• If they now need less money, and update the amount they need;
• If they no longer need to receive a mincome (e.g.: the mincome is now lower than their stated income), we should change their income details to say "Do you make at least x a month? Yes I do" and leave the pledge at $0.

Mincome changes, user was pledging:

• Their pledge remains the same unless they specifically change it.

EDIT by @taoeffect: We automatically/programmatically adjust the user's need as above, and where it makes sense, we'll additionally ask the user if they make the new mincome $X amount, and then proceed through the normal "Income Details" flow to adjust them based on the user's answer. See for details on this: #1125