Easy to mistake "m" duration prefix for minutes when it actually means months

It's a very easy mistake to type something like this:
`timew start 5m`
to mean "begin tracking something that started 5 minutes ago".

But in fact, it actually means "begin tracking something that started 5 _months_ ago".

(In that particular example, you would most likely be prevented from tracking that time due to overlapping intervals, but in other situations this could be a big mistake.)

What if, when you first use "1m", Timewarrior asks whether you mean "1min" (minutes) or "1mo" (months)? That will then become the default interpretation when you use "1m" the next time.

(People who are used to typing "m" for months and "min" for minutes could continue to do so, while people who are used to typing "m" for minutes and "mo" for months would be saved from making a potentially disastrous mistake.)