Feature: Better help messages

[kazad]

The info box now makes function suggestions as you type:

Without being annoying, the basic logic is:

• If you start a row with a valid function name (sum, total, PV, etc.) it will show the help
• If your row does not compute, and has a few words that match a function name and description, it will suggest that function:

The goal is to be helpful, not noisy. We'll see how this goes!