XLSX documents from office 2016 can have a percentage format of 0.0%

[exptom]

I've just run into an issue where the formating code on a cell is unknown. It is formated as a percentage with 1dp in Excel which shows up at '0.0%' on the call to $cell->getStyle()->getNumberFormat()->getFormatCode().

PHPExcel currently only has these format code constants:

	const FORMAT_PERCENTAGE					= '0%';
	const FORMAT_PERCENTAGE_00				= '0.00%';

I think a new option needs to be added:

	const FORMAT_PERCENTAGE_0				= '0.0%';