Read daily weather before the simulations

[dschlaep]

Historically, the simulation loop was obtaining daily weather values for one complete year at the start of each simulated year (SW_WTH_new_year()) and then at the start of each simulated day, _todays_weth() was providing the weather values for that day (either from an array, or if missing, from the weather generator) to the simulation.

Now, we prepare all daily weather for all years before the simulations:

1. read_all_weather() reads values from files (or uses the weather generator; or, if rSOILWAT2, obtains values via memory from R) and fills in values of all_hist -- before the start of the simulation loop

   • Incorporate current functionality of _todays_weth() in read_all_weather()

2. SW_WTH_new_year() and _todays_weth() are no longer needed -> delete

3. SW_WTH_new_day() will grab values out of all_hist (instead of calling _todays_weth())