Perform constrain before assignment to t for the WaterLevel reading.

This will ensure that the unsigned long t does not get assigned a
negative number.
Finish removing separate constrain for WaterLevel reading
Merge branch 'waterlevelfix' into current
Added backward compatibility for WaterLevelATO when Multi WL is enabled
close #184
Merge branch 'waterlevelfix' of https://github.com/lnevo/Libraries.git into dev