new keywalk option mode

[smarteam]

It is clear from documentation that diagonals are not used by default, but I guess an option to turn "ALL" is a little bit excessive and smth. in-between needed also.

Looking at a standard 104-key keyboard (https://en.wikipedia.org/wiki/Keyboard_layout#/media/File:ANSI_Keyboard_Layout_Diagram_with_Form_Factor.svg) it can be noticed that, if starting for example from letter "s" there is an direct "connection" with diagonal letters "e" and "z" and letters "q" and "c" are a little bit distanced which could lead for direction to less likely be chosen for "walks".

Can we have an option (like -"c" for "connected/continuous") to turn on --keywalk-south-west and --keywalk-north-east but without other two remaining diagonals? Yes it can be achieved with current options set, but I'm here speaking about usability side :)