Add breakcolumn options

[kluska]

breakcolumnfreeplace: 80% //will mean that breakcolumn will be ignored if there is more than 80% free space below breakcolumn div inside considered column.

sometimes you can have 1 row of text before columnbreak div.

It could be I think simply done by checking breakcolumn div offset relatively to its colomn and dividing it by column height. If it will be bigger, than value from options, breakcolumn would be ignored.