ExcelRangeBase.BorderAround should have the option to override borders on conncting cells.

[JanKallman]

Using BorderAround does not set the set the border style visually in Excel if a connecting cell has a border style wider than the border style set.
For example if the cell above has BorderBottom = Thin And BorderTop is set to Dotted, The Border will be Thin as Excel overrides with the "widest" border style. EPPlus should add the option to clear or set the border style to the same for connecting cells.