refactor(columns): Use momentjs for column handling

This is a big refactor in column handling using momentJS features.

view-scale now supports any of momentJS unit, like year, quarter and minute.

headers-* options have been dropped, in favor of headers and headersFormats (see README).

This drops support of everything related to working hours, weekends and column-sub-scale. Those options will be replaced by #126 and #123.

Close #79