Import Images from Excel cells about csv2rw

[farling42]

Probably only need to get ExcelXlsxModel::data() to return cell->value() if !cell->isRichString()

[farling42]

Within Excel, images aren't stored in a cell. They are separate Illustrations that just float above the cells.

[farling42]

Won't fix, as there isn't a logical method for choosing image over cell contents - and images aren't always overlaying just one cell.

[farling42]

The QtXlsx library has been patched to allow image information to be read from the file.

V2.18 adds support for reading images directly from XLSX files.

Each image in the XLSX file has an ANCHOR position, which references a row and column in the spreadsheet. This will be used to determine the cell in which the image will be stored (replacing any text that might also be in that cell).