add enumerating all submasks

[shinichi1729]

Title: Implemented Bitwise Fast Enumeration of submasks

Description: I've implemented a fast enumeration method for all submasks by taking advantage of bit properties.

Example: n = 13 (1101) s $\in$ {13 (1101), 12 (1100), 9 (1001), 8 (1000), 5 (101), 4 (100), 1}