Incorrect addition of column header and footer when adding a column by index

[Kachiro0121]

Incorrect Addition of Column Header and Footer in addColumnTo(int index, @nonnull ColumnProperties columnProperties) Method in BoardView Class (Line 946):

The header and footer are incorrectly added to the mHeaders and mFooters lists because mHeaders.add(columnHeader) (Line 1049) and mFooters.add(columnFooter) (Line 1060) do not use the specified index. This results in incorrect retrieval of the header or footer by column index.

[woxblom]

Ok, please make a pull request with the change

[Kachiro0121]

#215

[Kachiro0121]

Thanks for the quick response