COMMON: Rename ConfigFile to INIFile.

This clears up that 'ConfigFile' is actually a class handling only INI-files.
COMMON: Remove outdated comments on INIFile.

These very old comments claimed that ConfigManager uses INIFile. This is not
true however. Thus removing them should clear things up a little bit.
COMMON: Remove commented out include in config-manager.h.
Merge pull request #373 from lordhoto/ini-file

Rename ConfigFile to INIFile and remove outdated comments