Added some test cases
add_person() open_file() print()

open_file (): Works as expected.
need to implement decrypt functionality
print (): Well it prints the open file. It is not according the
specification yet.
add_person (): Need to add functionality to search after already
existing person and signature needs to be unique.
read_file & get_sector

get_sector: extracts results from the 4 sectors that a row contains
read_file: fills a person with the information fetched from data.bin
with the help from get_sector.
p_add & p_print

added functionality
struct personal_data

added a structure that hold person data.
const filepath

according to specification, global constants have to be placed in a
header.