Allow for input with time-related naming

[BramDr]

Would like to see that the input-file string can contain formatting patterns that match the time of the current model timestep. This is especially useful for meteorological forcing inputs that often come in yearly NetCDF files.

A simple key-based format would be sufficient, and would also allow for user-customized formatting options (such as the number of digits). As an example: netcdf_file_name = self.preFileNC.format(year = currTimeStep.year, month = currTimeStep.month, day = currTimeStep.day, hour = currTimeStep.hour, second = currTimeStep.second, milisecond = currTimeStep.milisecond)

[BramDr]

Likely best to include this in the virtualOS netcdf2PCRobjClone function