Add bar.h macro wrappers for all functions

Renamed some functions
* bit_array_other_endian_cmp() -> bit_array_cmp_big_endian()
* bit_array_compare_num()      -> bit_array_cmp_uint64()

Added LICENSE file: CC0 (public domain)
Merge branch 'master' of github.com:noporpoise/BitArray
bar{b,w}cmp -> barcmp{b,w}
Renamed some arithmetic functions

1. Renamed functions <current name> (<old name>):

  bit_array_add_uint64  (bit_array_add)
  bit_array_add_word
  bit_array_add_words
  bit_array_sub_uint64  (bit_array_minus)
  bit_array_sub_word    (bit_array_minus_word)
  bit_array_sub_words   (bit_array_minus_words)
  bit_array_mul_uint64  (bit_array_multiply)
  bit_array_div_uint64  (bit_array_div)

  bit_array_add      (bit_array_sum)
  bit_array_subtract (bit_array_difference)
  bit_array_multiply (bit_array_product)
  bit_array_divide

2. Moved decimal functions within bit_array.c to match header file.
bar.h includes bit_array.h
Fix licenses in headers
Rename barcmpb -> barcmpbe
Fix README.md spelling typo