Implement separate scaling for up/down

[calvinmclean]

It might be nice to have more flexible scaling configurations that have different parameters for scaling up or down.

Some possible use-cases are:

• Only scale down, never up (or reverse)
• Limit scaling down to halfway, but allow scaling up to double watering
• Allow a larger range for scaling up if there is a big range of high temperatures

Implementation:

• Separate up/down range will allow to have more extreme scaling down for colder weather, but will prevent extremely high water use in summer
• Min/max scaling value can be used similarly to prevent from scaling too high or too low