Implemented ConfigSectionReaderBase and FileInfoExtension classes

Implemented a new class to handle sections from configuration file (ConfigSectionReaderBase).
Implemented a new class to extend System.IO.FileInfo class (FileInfoExtension).
New class to handle config files with user-defined section names

Implemented a new class to handle configuration files with user-defined section names.
Implemented code to handle mandatory sections to configuration files into ConfigReaderBase class.
Added new methods to get or check existence of sections by name into ConfigReaderBase class.