Add both 3 column layout to customizer

[bassjobsen]

The fix for issue #2 add a new 3 column layout. This layout can be use by setting the number of columns to 31. This option should add to the customizer too.

To do this the problem having 2 numbers 3 should be fixed. One solution can be to change their names in the customizer to b.e. 3a and 3b with their values 3 and 31.

The number is also used in shorttags for example [featured_products columns="31"]. Have to use 31 for layout 3b can be create an unclear picture. Maybe the shorttag parameter should be renamed to "layoutname" or "layouttype". Note the shorttag column parameter overwrite the default /settings column parameter.