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.

ENH: move implementation of non virtual methods to a source file to add them in the shared library in MetadataStorageInterface and MetadataSupplierInterface

ReadXMLToList from GDAL is not part of the public API. It can be used
when compiling libgdal without --with-hide-internal-symbols
switch. But libgdal from Debian and Ubuntu packages doesn't contains
the symbols. The adopted solution is to implement a ReadXMLToList
function for the OTB.