* Support for non unique sections. Enabled with the option AllowNonUniqueSections.
* Non unique section support for MapToStruct
* Non unique section support for section.MapTo
* implement ini.ReflectFrom() for non unique sections
* implement xyz.Section("xyz").ReflectFrom() for non unique sections
* Refactor suggested changes after review
* remove GetSectionCount
* do not initialize sectionList if NonUniqueSections are disabled
* add test for deleting all sections of the same name
* refactor mapAllTo
* refactor ReflectFrom
* fix some comments
* refactoring based on PR suggestions
* update DeleteSectionWithIndex error
* customization output delimiter
* rename KeyValueDelimitersOutput to KeyValueDelimiterOnWrite
* add test for writing with KeyValueDelimiterOnWrite
* bugfix: use '=' as the default delimiter on write
Co-authored-by: Chaliy Roman <cerebrum.ch@gmail.com>