The ZipHelper interface is now more generic and allow single files to be added.
It supports adding uncompressed files (for PHP7+), which is required to have the mime detection magic work with ODS files.
Also fixed a few issues with the created ODS file (thanks to https://odf-validator.rhcloud.com/)
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
Added top level methods on the Writer:
- addRowWithStyle()
- addRowsWithStyle()
Added a style builder, to easily create new styles.
Each writer can specify its own default style and all styles will automatically inherit from it.
For now, the style properties supported are:
- bold
- italic
- underline
- strikethrough
- font size
- font name
- wrap text (alignment)
