fix bug in AbstractExcelImporter.evaluateAllFormulaCells()

[jnunderwood]

1. AbstractExcelImporter.evaluateAllFormulaCells() references Cell.CELL_TYPE_FORMULA. Instead, it should reference CellType.FORMULA. I suspect this worked at one time, but Apache-POI has since been updated.
2. I have also added an optional argument to evaluateAllFormulaCells(boolean inCell = false) that will call evaluateInCell(c) if true. Otherwise, it will call evaluateFormulaCell(c). This fixes a problem I was encountering with formulas not being evaluated. I wrote this so that the default behavior has not changed, however, so it should not break any existing code.

[sbglasius]

Looks ok to me.