This function is made to initialize PHASE structure, which is the main Structure
to store phases info (amplutide, picks, SNR…)
WRITE_FLAG parameter is used to decide or not if the phase has
to be taken into account before writing it in a nordic file for example, at
the beginning it set to 1 because we consider all phases are valid (a priori)

Input:
len_phases : size of the info structure

Output:
PHASE : Phase structure of length len_phase