MS Excel: Add to SpreadsheetCellDAO background color information

[jornfranke]

Background colors for cells in Excel sheets are frequently used when human need to "annotate" an Excel sheet with structural information and this annotations are supposed to be processed by an application and put into structured databases/reports. For instance, colors can indicate column names and data fields.
Hence, HadoopOffice should augment the SpreadsheetCellDAO with background color information.
It can be retrieved from the cell using cell.getCellStyle().getFillBackgroundColorColor().getARGB

(Alpha Red Green Blue color value).

This color should be also written when specified and writing the data to disk.
Furthermore, low footprint mode should be investigated. Old Excel format should not be an issue. New Excel format should not be an issue if the stax parser is used (default). For the SAX parser there are several complexities involved.

This needs to be available on all supported platforms: Hadoop, Hive, Flink, Spark