Added the function ‘eval_2stage’ for the evaluation of the two-stage design by means of simulation

Added the functions ‘sensitivity_min_SSU’ and ‘sensitivity_min_SSU2’ to give hints about how to choose the value of ‘minimum’ parameter (minimum number of SSUs to be selected in each PSU). The first is to be used when a sampling frame of SSUs is available, the second when it is not available. These functions are in substitution of function ‘sensitivity’

Added the function ‘select_PSU’ to select first stage units (in substitution of ‘StratSel’, eliminated)

Added the functions ‘prepareInputToAllocation1’ and ‘prepareInputToAllocation2’ to produce the inputs required by the allocation step (the first in case no previous round of the survey is available, the second when at least one round of the survey is available)

Added a function (‘select_SSU’) for the selection of Secondary Stage Units

Added a function (‘sensitivity’) for the fine tuning of parameters

Added two functions (‘input_to_beat.2st_1’ and ‘input_to_beat.2st_2’) to prepare inputs for the allocation step

Added function ‘StratSel’ executing the PSU selection step

Fixed some bugs