All entities will now be created through a single factory (including the Writers).
Also, added a EntityFactory::createRowFromArray() to make it easier to create rows
This commit introduces Row and Cell entities, that will replace the arrays passed in previously.
It also adds support for Cell styling (instead of Row styling only).
This will improve the management of options and simplify some methods' signatures.
This commit will also help moving the code to a better state regarding Dependency Injection.
Remove num-columns-repeated and num-rows-repeated as it does not seem to be required (LibreOffice does not add them).
This greatly simplifies the writer and the XML output.
Added some optional attributes to help LibreOffice with cell values caching ("calcext")
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
