ISExcel Cells; GetString function may return an unexpected text value

The ISExcelCell object, GetString function may return an unexpected text value. For example, "664699.01" may return "664699.01000000001".

This can be due to the Cell Value actually begin stored as a "Double" Value Type, and in converting to a String a rounding issue occurs.

Other changes include GetDecimal and GetDouble now support an optional "decimals" parameter. This specifies the number of decimal places to round the value to. If not specified 4 decimal places is used.