Finish support for visual mode 'o'

This adds support for line and block support of visual mode 'o'.  This
finishes most of issue #611.  Still need to implement 'O' to completely
close out the issue
Added support for visual mode 'O'

This adds support for visual mode 'O' (:help v_O).  This lets swap the
column the caret is in during a block selection

closes #611