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.

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

When using ToJSON attribute to export metadata, the order the metadata
are exported depends on the platform. This is not a problem when
working with metadata, but the test (as they are currently made) need
a constant order of the metadata in the output file.

REFAC: move image list objects to a new module, because they now depend on OTBMetadata, which depends on OTBObjectList