Resolve SAR metadata interfaces

Refactor image metadata interface for SAR sensors. The metadata are now read by gdal instead of ossim. Concerned sensors are :

• SAR IMI: TerraSar
• SAR IMI: CosmoSkyMed
• SAR IMI: Radarsat2

The metadata parsed are :

1. For CosmoSkyMed:

• AcquisitionStartTime
• AcquisitionStopTime
• Mission
• Mode
• ProductType
• SensorID
• Instrument
• RadarFrequency
• OrbitDirection
• OrbitNumber
• Polarization
• Swath
• PRF
• SAR Orbits geom

2. For TerraSar:

• AcquisitionStartTime
• AcquisitionStopTime
• Mission
• Mode
• ProductType
• SensorID
• RadarFrequency
• OrbitDirection
• OrbitNumber
• PRF
• PSF
• Polarization for each band
• LineSpacing
• PixelSpacing

3. For RadarSat2:

• AcquisitionStartTime
• Mission
• BeamMode
• ProductType
• Instrument
• SensorID
• RadarFrequency
• OrbitDirection
• PRF
• PSF
• CenterIncidenceAngle
• Polarization for each band
• ProductionDate
• LineSpacing
• PixelSpacing
• NumberOfLines
• NumberOfColumns
• AverageSceneHeight

Three tests have been added, one for each satellite (see ioTvImageMetadataInterfaceTest_Radarsat2, ioTvImageMetadataInterfaceTest_TerraSar and ioTvImageMetadataInterfaceTest_TerraSar).