Fixes#682
When calling `Row::setCellIndex`, it's possible to create a Row with holes.
Instead of iterating over existing cells of a Row, we should instead use the cell indexes (from 0 to max cell index).
* Refactor readers to get a proper DI
Similar to what was done with writers, readers also needed to be updated to match the new way of doing things.
This commits promotes a better DI (factories, injection through constructors).
* Escapers should not be singletons
Instead, they should be proper object that can be injected where needed.
When converting an XMLReader node to a SimpleXMLElement, the conversion would automatically decode the XML entities. This resulted in a double decode.
For example: """ was converted to """ when imported into a SimpleXMLElement and was again converted into " (quote).
This commit changes the way the XLSX Shared Strings file is processed. It also changes the unescaping logic for both XLSX and ODS.
Finally, it removes any usage of the SimpleXML library (yay!).
Added ODS writer
Refactored XLSX writer to abstract some pieces into an abstract multi-sheets writer
Created an abstract style helper
Moved shared components around
