IniEncoder

[ffried]

This issue should track the interest in a IniEncoder. If enough votes are collected, we'll add a IniEncoder example, as well as doing some refinements to the existing implementation.

The following changes would be made:

• Add an implementation for IniEncoder.
• Parse INI content into an enum (instead of Any) to simplify encoding & decoding.
• Allow sections with the same name as keys of the top level INI part (essentially resolving https://github.com/sersoft-gmbh/Codable_Macoun17/blob/master/ParsINI/IniDecoder.swift#L26)