Added a new method addBackwards to adds text to the kill ring product of a 'backwards' kill. This permits that consecutive backwards operations or combination of mixed backwards and forward kills to leave the ring in a correct state. Previously if you had 'hi there' and did backward-kill-word twice followed by a yank the result was 'there hi'.
Adds support to preserve in the kill ring the text removed after a UNIX_LINE_DISCARD or UNIX_WORD_RUBOUT operations.
Added a bunch of new tests using the ConsoleReaderTestSupport infrastructure.