* 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.
* Add option to preserve empty rows when reading an XLSX file
* Add option to preserve empty rows when reading a CSV file
* Add option to preserve empty rows when reading an ODS file
Instead of the hasNext() / next() syntax, readers now implements the PHP iterator pattern.
It allows readers to be used with a foreach() loop.
All readers now share the same structure (CSV is treated as having exactly one sheet):
- one concrete Reader
- one SheetIterator, exposed by the Reader
- one or more Sheets, returned at every iteration
- one RowIterator, exposed by the Sheet
Introducing the concept of sheets for CSV may be kind of confusing but it makes Spout way more consistent.
Also, this confusion may be resolved by creating a wrapper around the readers if needed.
-- This commit does not delete the old files, not change the folder structure for Writers. This will be done in another commit.
