Implementing (next/previous)(Set/Clear)Bit()

[srounce]

A reasonably DRY implementation of the following methods:

• http://docs.oracle.com/javase/7/docs/api/java/util/BitSet.html#nextSetBit(int)
• http://docs.oracle.com/javase/7/docs/api/java/util/BitSet.html#nextClearBit(int)
• http://docs.oracle.com/javase/7/docs/api/java/util/BitSet.html#previousSetBit(int)
• http://docs.oracle.com/javase/7/docs/api/java/util/BitSet.html#previousClearBit(int)

Need to write some unit tests, but has been manually tested, and all seems good.

[srounce]

Will update source branch with:

• Fixed conflicts
• Updated README.md with methods listed