Validates Microsoft Project-type duration entries. Accepts a number and a unit. The number part can be integer or decimal. The unit can be several variations of weeks, days, and hours: e.g., w, wk, week, ws, wks, weeks are all valid. Whitespace between the number and the unit is optional: e.g., 1d, 2 days, 3.5w are all valid. Captures the number value in a group named num and the unit string in a group named 'unit'.