Implement new functions operating on two sets of rules.

    Added functions:
     smack_accesses_union()
     smack_accesses_intersection()
     smack_accesses_complement()
    The above functions implement boolean set operations on sets
    of Smack rules.
Implement a command line tool "smackpolicy"

The command line tool provides functionality of libsmack functions:
    smack_accesses_sort()
    smack_accesses_union()
    smack_accesses_intersection()
    smack_accesses_complement()
operating on files containing rules and writing output to given file.