Aalto spring2019

The tracking starts from the first day of the weather data, and tracks
if enough days have passed. If enough days have passed, the effect of
tillage will be changed from Tillage to TillageEffectAfter parameter in
the configuration file. TillageEffectDays sets the number of days for
this to happen.

If the effect is not wanted in a model run, it can be disabled by
setting the timeTillageEffects parameter to false. By default, the
effect is in use.

Inn FinnCerealModels the different risk levels have been added. Now the
model will give a low level warning if accumulated risk is over 50 and a
high level warning if the accumulated risk is over 100.
The model-constants has been modified to use new values for calculating
the accumulated risk value from the daily risk value.