Make the amount of items configurable per column

Currently, Kanabanboard macro displays a limit of 50 tasks. As a consequence, some items you would expect to appear in the kanban board, are omitted.

The macro could be improved by allowing the user to set the limit - this will make it known that its possible that not all the items will be displayed.

 
A suggestion for this improvement would be that the limit should be applied per column rather than for all the columns. For example, If the user desires to display a kanban board with only two columns, setting the limit to 25 will display a maximum of 50 items, 25 per each column.

The current behavior is that the limit is applied before the filtering per category type is done.

For example, If there are 50 todo tasks, 10 done and 20 inprogress, a kanban board macro with all the columns will omit a number of tasks because of the default limit. However, if the user wants the kanban to only display columns for "inprogress" and "done" is it expected that all the tasks of these statuses are displayed, since 10 + 20 is less that the default limit of 50. This is not the case currently.