1.8.0: Setting cell fieldtype automatically to formula

[remyw]

The following code should be disabled in Cell/DefaultValueBinder.php. You should never want "automatic" formula fieldtypes:
} elseif ($pValue{0} === '=' && strlen($pValue) > 1) {
return PHPExcel_Cell_DataType::TYPE_FORMULA;

General text fields starting with '= blablabla' will generate errors. If it's a cell with a formula, it should be explicitly set via setValueExplicit()