Remove unused commented code.
Rename OTB_xxx from otbGeometryMetadata to simply xxx.
Optimize constructors for otbGeometryMetadata::GCP.
Use reference to MetadataSupplierInterface instead of pointer in
ImageMetadataInterfaceBase::Fetch.
Use keyword 'using' in place of 'typedef' in GDALImageMetadataInterface.

The class XMLMetadataSupplier belongs to a public hierarchy,
it should not be possible to copy it.

Changes in otbMetadataSupplierInterface: method
- GetRessourceFile now takes a parameter
- new method GetRessourceFiles

Add a new Fetch method for the Extra metadata. And
the other Fetch methods had an issue with fetching the
metadata for the bands.